For what it's worth, I updated to v0.5.5 when it was released. As part of my testing, I also spun up several virtual machines where I installed Sigil and CustomCleanerPlus v0.5.5. I saved an epub3 version of my test line. When I ran CustomCleanerPlus on my test epub, I got the same result on all 3. No other plugins were installed on those three VMs.
Please note that this behaviour is consistent with any of the tags I tested surrounding a space and even when I tried <div> </div> which was collapsed to <div/>.
See the attached images for the before (Mac OS Sonoma 14.1.2 only) and the post CCPlus run on all three VMs.
I still believe that removing the tags and leaving the spaces would be the correct behaviour while the actual behaviour of removing the spaces and collapsing the tags in incorrect.