Ah... I can tell you what that is, that is part of our little 3D printed mounts that we put the boards on to raise the board whilst we coat it, sometimes the legs break off and we have to print new ones.. it looks like you've got yourself a limited edition 'unpushed one', if you want to just get a screwdriver and push it out.
I will speak to our conformal coating team and make them sit through a 2 hour AI generated video on how to make sure all 4 holes are usable before we ship the boards to customers.
Spoke to Dom, the black plastic is coated both sides and hard as rock - tried a screwdriver before I posted (should have said that). He advised I should drill it out.
For those reading this in months when this appears in a Google search.. Dom said drilling this out was a good idea in VERY limited circumstances, for regular use Drilling is not advised, this is an early Baldrick8 release and we've changed our process (twice?) since then.