I must assume the OP's purpose is to deride the chain stores and their misleading fish labels. If so, this is a 1-2 decade old news.
Unfortunately, the changes to reflect the reality are indeed slow to come, complicated by the fact that some IDS indeed grow to significantly smaller sizes versus others.
This has been discussed in some depth for instance here:
https://www.monsterfishkeepers.com/forums/posts/6054229 To this thread, I must add my new experience that properly housed IDS is, IMHO, unlikely to grow to only a foot or so. I had had an albino IDS who I thought was the runtest of the runts and grew to ony 8"-9" after 3 years with us. It too was exceedingly flighty in its "spacious" 240 gal 8x2x2. Eventually I rolled the dice and placed it in a 4500 gal. It paid off. The IDS started feeding better (it fed before seemingly more or less ok) and started growing quickly. It was a few months ago and the fish is 1.5' currently and not stopping.
Hence, I must surmise that perhaps all or most of the reports from MFK-ers that their IDS refuse to grow properly for years are related to the housing - their fish, just like mine, were stressed in too small tanks, by too boisterous or harassing tank mates, or somehow else.
The thread on our current IDS:
https://www.monsterfishkeepers.com/forums/posts/7639582