Possibly. When I worked at a place that designed a "simple" chip that was just a more energy efficient and very parallel version of its FPGA, the fab that was contracted to make it insisted on validating it themselves. It consisted primarily of a lot of copy-paste of the primary logic to build as many paths as would fit on the die. They described it as "unusually dense" and, I heard they later said that they'd never seen a design that dense. The validation process was partly described as people manually driving a car through a 3D model, making sure there were no unexpected junctions or other divergences. This process took months longer than their initial estimate, allegedly due to the density.
I guess you could say this was "under the umbrella of the chip-maker", though we had little say in it aside from pressing them for progress as our final product's shipdates came and left. When we finally got the first samples, power consumption was, I think, an order of magnitude higher than expected. Our lead engineer struggled to get it down without going to a smaller process that we could barely afford (and given the delays already, could probably not have afforded to wait for). We thus thought we had working logic, but our case designs were scuttled. After enlarging the cases to accommodate extra cooling, our base unit was more than ten times taller, and our next size up, while the same height, was three times longer. Highest units had a water cooling system[1].
Our QA was able to find other sorts of flaws, like misprinted unpopulated circuit boards, software faults on the host, or when we received shoddy interlink cables that either melted under test[2] or other cables that scrambled communications[3].
All of which is to say, that many other pressing issues can interfere with doing what you feel you ought to be doing. At least at our scale. I can't speak for the likes of big guys like Intel or AMD, but it's possible that unfound faults or known unpatched flaws can ship because resources were committed elsewhere or fabrication leadtimes preclude waiting. This is not to say that shipping a security flaw is okay, but rather that sometimes you think you've done you're due diligence, or sometimes your choices seem to be "Ship, ship late, or never ship.". The answer you pick can be existential, so you hope you've picked the least bad option.
[1] Misbegotten, because "beauty of the promo images".
[2] Conductors much thinner than spec, not initially observed because both ends were fitted with moulded plugs.
[3] Longer than spec, initially recieved with enthusiasm by assembly staff, before an engineer investigating a difficulty saw them and exclaimed, "No-no-no! That's longer than I am tall! Stray capacitance alone will kill the communication.". (He uncharacteristic'ly exagerated here. While they were three times longer than expected, this was at most .40 times his height.)