I can visualize an engineer making that mistake way more than a UX person.
"I need something to enter dates, oh here's a calendar widget library. done."
The reason for product to own UX more is they should be more connected to the 'why'.
Whoever owns the UX should be putting the thinking effort into how that behaves. Things like this happen due to a) inexperience with whatever UI construct is being presented and/or b) not enough thought being put in to the usability of that component.
A developer is generally going to be more hands on with the resulting UI (checking/testing etc..) Whereas, a designer has more than likely mocked it up in InVision/whatever and then done surface level checks
And product managers will be hands on with the product but, well, they shouldn't be trusted with UI/UX/anything but the description of the problem they want solved :-)