O_STOPINTS has nothing to do with the STOP opcode (at least according to the JTRM); the OP ignores anything in bits 3-63 of a STOP object. It looks like it should be some kind of interrupt control bit, but it matches nothing (the closest is INT1 [$F000E0], but it should be $4 in that case instead of $8).
Dunno what to tell you other than, what do you need it for? Does it really do anything?
N.B.: STOP is *not* a pseudo-op, it's a geniune, bona-fide, real as real can be opcode. : )