Tested this, can confirm units can be pushed into Lava but not into chasm, this behaviour is correct.

Hmmmm, while it's certainly a very minor UX issue I don't think that there's a major problem with it. Players can just move their rally flag, it'd be a fair bit of work to change rally on arena and prison.

Likely you're not meant to be able to place constructs in which case the tooltip would be incorrect. I'll double check this on Monday.

Indeed Old Cat is right, this is working as intended.

Will check intended behaviour :)

I'll have to check the intended behaviour on this.

Unfortunately this is a technical limitation, in addition to it actually being desired by most players. (We've received regular requests to make unit shields less obtrusive, forcing them to appear above level geometry even if possible would be counter to those requests.)