The USCG practice when inspecting vessels that can carry over 6 is to ask for a thru hull or two be removed for inspection.
Of course this is not required for a non inspected vessel, but if the USCG has found it to be a worthwhile practice , sealing thru hulls should be done so the can easily be inspected. Not installed with glue, but with sealant.
4200 and the proper removal tool will make inspection a few min job , should you desire to look.