The way the chuck locks into the sds hole does not allow any fore and aft
movement, therefore the little hammer inside will smashing against an
immovable object and will get damaged.

I think you're mistaken there.

Well , that is how my wickes sds drill and chuck design is, so I assume
others are similar. The chuck adaptor which fits into the sds slot has only
one depression in the side, this effectively locks the adaptor solidly into
the sds chuck of the drill and allows no fore and aft movement (unlike a
drill bit, which can float )

That'll be the cheap crap you've bought there then. None of my SDS to
conventional chuck adaptors, nor any I've ever seen, have been any
different in their design to standard SDS bit shanks.
...

SJW
A.C.S. Ltd.