Why can't you glue aerated concrete?

[Fred vom Jupiter]

I'm considering investing in glass blocks in insulating glass when an old window needs to be replaced. At Byggmax, they are very clear that insulating glass blocks must be mortared and cannot be glued with profiles. It's a shame since it's very easy to glue, but why can't it be done?
Byggmax warns of frost damage, but why would it be worse with insulating glass blocks than with regular glass blocks?
Wouldn't there be a thermal bridge with consistent mortar instead of a foam strip between the blocks?