Please note that even if the gearbox is perfectly legal mechanically, for you to use it on a competition bot, it must be purchased from a legal vendor.
Section 4.1 (pages 3 and 4) sets forth criteria necessary for a company to qualify to be a legal vendor. Aliexpress.com may not qualify. In fact, I seriously doubt it.
Of course, it could be argued that none of the vendors we think of as FIRST vendors actually qualify per the written criteria. (Not going there in this post.) This section of the manual is probably one of the most ignored rules in FRC. They should just delete it.