As long as the finish is protected, this shouldn’t damage speakers.
But as mentioned above… it will completely screw up the sound. I used to own a pair of Olympica 3. They need distance behind and on both sides… and definitely be upright. The external cabinets are purposefully designed in all aspects.
I would trade them in for some cheap box speakers made to be close to a wall… although being enclosed we make them less than optimal.