When I activate the elytra and let it glide to the ground, then I walk into a block with an empty area underneath it forces the player into crawl mode, despite not gliding into the empty area.

The exception is that when walking into a block after activating elytra, the player shouldn't be forced into crawl mode, instead you just keep on walking.

This setup is very easy replicate. Here is a video demonstration...
https://1drv.ms/v/s!AuGXzZh_yMrOhDKSgje33OjaT4BC?e=0u583X

For all I know, this might work on other platforms... But idk.