According to the link Formosa Neijia posted, The author in that link came in contact with Taijiquan in 1925 some decades after Yang Luchan passed away. Things can very well change in a couple of decades, especially if things find it self in a different environment(Beijing vs Chen village)
The Yangs while in Beijing seemingly develop variations of push-hand exercises, while in the village as I suspected the sparring was simpler or perhaps should say more direct, that direct way might have been quite intense in Yang Luchan Chen village days, one had to struggle with it till the day one no longer got a nosebleed doing it.
However while teaching the upper class in Beiping one had to do things carefully.
As Bao point out, the upperclassmen didn’t like it too strenuous....
However, about the form practice, my personal idea about that, the form practice of today’s Yang Taijiquan is the same as YLC did....How did I come to that conclusion? well just practice long enough and most importantly right enough one will instinctively understand that.
.
(Personally I think that is a much more reliable research method than digging deep into scriptures, although that can be fun to do too)
Things kind of hidden in plain sight, one just have to have the key of right intent.