the flimsy bumpers are ok for a spare tire but they don't sit on the bumper the same way a bike rack would.
the spare tire is right up against the back of the trailer and bumper. so any movement is close to the mounting point.
a bike rack holds the bikes out and away from the bumper and rear of the trailer. this is like holding a weight out with your arms outstretched. the physics involved between a loaded bike rack and a spare tire on the bumper are completely different.
that loaded bike rack will flex back and down on the bumper mounting point. like pulling a big vertical lever.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC