I liked the article, again I've heard this from my own teacher and other sources, I think that if you are training seriously you'll be told about this kind of thing anyway. But I think it is good Sifu Yang is making this kind of information public too. I think people should be more open about Xing yi in general. But I do agree with Graham that increasingly there are silly arguements over trivial matters too.
To explain a little of what I think and maybe answer some of Bao's questions.
When you begin training in Xing Yi, usually with standing pile exercises such as san-ti and also basic drills such as Wu Xing Quan the emphasis is all on structure, physical shape, alignment, maintaining integrity. This is essentially conditioning the outer to allow the inner to work better later. If you think of qi and jin like water in a hose then if you step on the hose or the hose has a kink in it the water slows down or stops. Its all about making the hose kink free before you can turn on the water. If you've got a tidal wave of internal energy but can't send it down the hose then the other guy feels nothing. But even if you don't have lots of internal energy you can still slap the guy with the hose and it will hurt them
In context, a guy with a spear if they are really good can send jin down the spear to the tip and tear through someone's armour, a guy with no internal energy can stand with the spear in a strong structure and still send it through someone, no qi/jin required. You can fight using no internal energy with Xing yi, in most situations you probably don't even need it anyway, but when you do learn it your effectiveness increases. An external guy can still beat an internal guy though, it doesn't matter how much qi/jin you can generate if you don't also have strategy, position, timing etc.
But don't confuse this stage of training to be entirely "external" the strategy and principles of Xing Yi at this level is still internal based, i.e. no force vs force, use of similtaneous attack and defense, every action can be modified to the situation, keeping centred and relaxed etc. it is just that this part of training lacks the use of what people would call internal power. In another way if you look at the 6 harmonies, the 3 internal are not emphasised until the 3 external are proficient so xin, yi, and qi are put on the back burner until the body mechanics and alignment are good enough.
Personally I feel that "hard" is not necessarily the right word to use, "obvious" is a better word as you are looking to create an obviously robust structure first, a vessel to contain internal energy. My training is still very much at this obvious level but i still practice relaxation and body awareness (in fact body awareness is a big part of this level of training).
The terms ming, an and hua are just general categories, you find that they overlap considerably and some people may learn an jing level concepts very early whilst still training ming jing. Often, as in my own case, you are not told this is ming, this is an, you just do what your teacher tells you is necessary for your level of ability and understanding. I was not told anything much at all abotu qi or jin for my first 3 years of training and since then have only been drip fed small amounts with the onus on trying to work things out for myself.
I think that certain schools do things differently, I know that some Yi Quan schools spend years on standing pile exercises while others focus lots on shili which is more about internal work. Xing Yi there is a progression,
develop the base using Wu Xing and associated practice, you
learn to use strategy and energy using She er xing and related practice, and then you
fight which is real Xing Yi.
In terms of transition to the more internal work, I'm beginning this now, it is hard work but i'm not "re-learning" anything, some things do get discarded but in fact you build upon the skills you've already gained and refine them.
I know from doing a bit of tai chi that they often do things a little differently, but there is still a progression in the tai chi form, at first you learn the movements, then make sure they are correct, then add in some roundness, then the continuous movement, and then later things like body lightness etc. It seems to me at least that in tai chi there is more freedom of expression and a lack of structure at the expense of learning more about energy and movement when you first start and then you slowly add the discipline and structure. In Xing Yi you kind of do things the opposite way around learn the discipline and technique first and slowly loosen the reigns so that you keep that discipline but can apply it freely. The end result is to get to a very similar place but the methods are slightly different.