The trap door on the Enfield design was originally for Military maint/replacement,,something surely needed quickly in their situation and for the storage of the oiler and pull-thru.
It's a neat little detail, but again I wouldn't get hung up over it. How many times do thru bolt stocks on other common sporting fireams need to be instantly accessed.
On the Enfield, the butt stock is the last thing to come off anyway.
The entire rifle can be serviced with the butt stock in place.
On the original Metford/Enfield design set up,,and the earlier SMLE , the forend has to be removed before the stock thru-bolt is even turned. If you don't follow the sequence, you crack the forend.
The square shape of the end of the thru bolt locked into the square hole in the back end of a plate in the forend.
A thick, tight fitting leather washer pushed down on top of the thightened thru-bolt in the stock made for blocking un-authorized attempts at mucking up the fit-up.
It also acted as a dampener when dropping in the brass oiler in the pocket.
You could always carry your hunting license in there, or an extra cell phone battery. I guess a dime or quarter for the pay phone is somewhat outdated,,
A well made trap door butt plate, or grip cap does have a special look to it.
Like most things custom, I guess we really don't need a reason.
Nice work Newton 1131!
