Classical Tai Chi uses a "compact" and "tight compact" form

If one searches the Web they will undoubtedly find many styles of Tai Chi that state they are "small" or even "compact".  It becomes apparent that there is no universally accepted definition among all parties of what these frame sizes mean.  One styles "compact" looks like medium or even large to someone else.  One can even see well known masters doing forms or even push hands in what can only be called a Compact Form by anyone viewing it. There are many videos of older masters in the Wu Style that show them in a compact stance while doing push hands.  The same videos show them uprooting students to the point of the students falling down.  Seemingly, the master is using some hidden strength...an "internal" strength. To put this issue to a temporary rest, I will quote my teacher who states: "To attain that type of capacity requires many years of training beyond proficiency in forms training".

 Now is it not quite poor reasoning  and really just conjecture to think that any style  or even any individual does only one frame or size of Tai Chi?  The questions still arise however, then we may even see the same masters doing a larger frame form.  Thus raising  further questions:  Did this master, did that master,  learn compact form 1st, now they are showing us their large frame?  Did they learn large frame first and do they really know compact?  Can we assume from these photos or videos that Classical Tai Chi is not the only Tai Chi that does Compact Form?  Putting aside the definiton of compact for a minute, let us examine what it means to be "compact" in Classical Tai Chi.

I quote largely from "Uncovering the Treasure" by Master Stephen Hwa:  "Wu chien Chuan did not start Young (Young Wabu) on Large Frame probably because Young was an accomplished external martial artist with a well developed external structure and lower body foundation already".

• Such difference in appearance also signifies how the Tai Chi movement is done
• Large steps/low stance requires use of leg muscles to push the body in all dimensions
• Compact form primarily uses core muscles to pull the body forward and upward
• Internal discipline, internal movements cannot be taught to students in large frame
• Large frame uses large swings of arms at shoulder, outstretch (telescoping) arms

Is it not now clear what defines compact form in Classical Tai Chi is the use of "internal discipline" or "internal energy" as explained once again in the Classical Tai Chi "turning move" videos attached here?  Please see "turning move" video 1 and 2 on that page.  What is not conducive to "internal discipline" or "internal energy" is also explained.

Now I have a couple of questions in light of our clearly defined manner in how a compact form can be performed:  Why do these famous masters demonstrate compact form on places like Youtube?  Specifically,  If a compact form can only really be performed correctly by using "internal discipline" and core muscles, shouldn't this be announced and taught to the world unequivocally and ubiquitously by all the famous masters?  How does not announcing this knowledge and making it obvious, contribute to promulgating  and most of all saving the art of Tai Chi?