And to get back to the original OP, before my bilateral mastectomy (due to breast CA, which anyone who wants to search my posting HX can confirm), I regularly wore very tight sports bras owing to being fairly big busted and also a runner, and I can confirm, that weight loss/gain/pregnancy and breastfeeding aside, my breasts never changed size or shape.
And none of the sports bras I've ever purchased have had any sort of warning on them that my breasts could change shape or size. Christ, if they could shrink your breast size, many many of my friends could have saved $$$ on breast reductions if that were the case.
To say that sports bras are equivalent to breast binders is naive and disingenuous at best, and at worst, dishonest and downright dangerous.
Binders for children are dangerous and abusive and should be made entirely illegal (If they aren't already).