How is this for a possible scenario:
The Capt. of the 777 was told J9, didn't like that, it suggested to him that ATC was telling him all the R/W he needed. Had the ATCO asked him if he could accept J9 to expedite he may have been happy to take it? But he asked for J10 and when it became clear that it would delay him he was then prepared to accept J9.
Possibly a bit of ego creeping in here?
Just a thought.
(36 years flying, mainly LH, including HK and the 747).