Yes, it will prune on the fly if you have it set to the prune mode. It should be > = 550.
There are more details in the release notes. To enable block pruning set prune= < N> on the command line in nf where N is the number of MiB to allot for raw block & undo data.
The minimal value above 0 is 550. 14) when they added a " manual prune mode" that allows you to fiddle with it yourself. As most likely the new hash would not fulfill the difficulty requirement, the proof of work would have been destroyed. Note: It can be 550 any value as you like.