Think about the J box in an old work can light and use that for guidance. The operative words are 'building finish". If this is something an electrician would be comfortable removing for access I think it is accessible.
Sorta one of the grey areas again. Based on the definition, with no damage/removal of building finish, it is IMHO, NEC compliant.
From a guy with tools point of view......he finds note of splice point/box location, finds the right recess can & drops out the interior. He eyeballs the 4x box, mutters a few words & proceeds. He has to work by 'feel' or 'brielle' with one hand.
As an AHJ, that is an 'acceptable' scenario; do I allow it? Short answer, yes. However, most guys work the 'splice' into the fixture wiring compartment/box.
My scenario includes a location currently with 2 three-ways. Suddenly in the middle of a more open kitchen. Fortunately,I believe, from a walk thru yesterday that I may need only extend 1 3 way switch setup. The rec. are near or at the end of the ckt.,so re-feeding from the basement may not be too bad.
By the way- This is my 1st job with an official complaint of the additional cost for an AFCI breaker- due to 'modification of a ckt." Can't wait for the first panel upgrade due to fuses for 1 additional rec.
As usual I am late but we have in the past installed a splice box above/near a recess light. We would also leave notes inside the can telling someone else that there is a splice box above/behind the recess light.