Well, unfortunately history has proved otherwise.
Asrock, Gigabyte, Asus have all at some point been guilty of marginal 140w, even 125w support on cheaper motherboards, usually in the hope that the majority of people won't load them to the brink in poorly ventilated cases, and/or not properly taking into account the higher current requirement of low Vcore, high TDP parts... (typically higher core count SKU's)
And it's not that they intentionally designed the board to be sub par from the outset, it's just that exuding new, higher TDP SKU's from their support list is going to lose them sales, and with no clear boundaries, it's a bit of a case of "monkey see monkey do" when a new SKU support shows up on a competitors equivalently priced motherboard.