I have not looked carefully at the following 2018 study, but you may find it interesting:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6160034/The use of “randomized, assessor, and statistician blinded, parallel-controlled trial” is what one would want, but the control group is just “unaltered lifestyle,” which is OK for just seeing benefits, but not parsing out the contributing factors. For example, a seated meditation group may have been good to compare with as they would have the instructor/instruction factors similar to the standing qigong group (controlling for the Hawthorne effect, etc., but not doing something that would be expected to improve one’s balance...), as well as the contribution from meditation without the held standing postures. There are no real controls that look at various aspects that they examine like balance, breathing, psychological health, mobility, and other “quality of life” issues.
One can probably see if there are significant effects (changes, improvements) from standing post qigong practice when compared with “subhealthy” individuals who do nothing differently than normal (i.e., remain “subhealthy”). But we cannot tell if those improvements are from things like the Hawthorne or placebo effects, general health improvements, etc., or if they are due to the specifics of the standing posture qigong.