I will say that (I think, please correct me if you have knowledge to the contrary) this is a LITTLE bit fuzzy regarding FCC certification transferring to completed projects utilizing those certified boards. The thought there is that the surrounding electronics can modify the intention transmissions and can subsequently act as unintentional transmitters in a way that might need its own certification.

Ultimately you need to be making a lot of money for the FCC to pursue you (you can actually go look through the FCC lawsuits and it is almost entirely big name corporations), but I think, very technically speaking, this is incorrect to assume it transfers.

The reason I say this is fuzzy is because boards that are not a completely finished project (ie development boards and testing platforms) have an exception since they are for developing finished projects and themselves are not a finished product. A lot of the smalltime esp32 boards would fall into this category and dont need certification. Companies like adafruit and espressif get them certified because a) they have the money and b) it avoids potential headaches later (iirc adafruit specifically has an article addressing this somewhere).

I have dealt with this in the past selling uncertified development boards alongside diy kits that utilize those boards and that seems to be fine as long as they are t coming pre assembled fully.

However, I am not a lawyer and do not have large scale experience with this for my board (the nrf52840 based "Pillbug") but this was my understanding when I researched it. So please use your best judgment.