Today I looked at the Sandy Drifts record by @Sm4sh and learned that the glitch works as long as you are respawned in the air. I tried this trick out on the eight courses that were Glitchless only and found out that it's possible on three of them.

Pinball Highway - There is a bump you can ride off at the end of the track. You can reach it in only one shoe boost after turning around at the finish line.

Deadly Route - It is possible to ride off the staircase at the end of the track leading up to the graveyard section. I think that it's barely reachable in three shoe boosts if you do them at the right spots.

Turbine Loop - You can ride off one of the two hills halfway through the track. You are in the air for a very short time, and sometimes you don't get any airtime, so this is the hardest one. Three shoe boosts are nowhere near enough to reach the hills, so I drove backwards to get there.

As for the other 5 courses:

Treetops & Highway Zero - Impossible The tracks end in a large fall, so you are completely blocked going backwards.

Shibuya Downtown - Impossible The track is completely flat; no way to get any air.

Dark Arsenal & Studio Amigo - Could be possible It might be possible on these tracks, as they have elevation changes. Unfortunately, the changes are so gradual that I wasn't able to get any air. I didn't try for very long though, so it could happen!