It would be nice to know more about the post, background.
Newer converters are really good, but if it fails, there could be some type of battery damage.
Only time I have seen deep cycle batteries crack, was due to poor maintenance and a weak charge. A weak battery in a Minnesota winter can freeze, and when they freeze they can crack. A strong fully charged battery will not freeze.
Wet cell batteries need maintenance. Twice a year, I pop the covers and add DISTILLED water if needed. Never any other type of water. The minerals in the water will do bad things to the cells, and they will fail. I would not doubt it could break.
I always keep my TT plugged in between trips. I just replaced my original battery 9.5 years old. I was fairly abusive on that battery. Converter failed when the TT was fairly new, stuck on stage 1 (??) high charge current. Boiled the battery really good. Had the converter replaced, and added distilled water. Lots of accidental to deep of a discharge. I always pull my batteries in the winter and make sure they get on the trickle charge a few time over the winter.
I would say, what ever that person posted was like a lot of stuff on the internet, take it with a grain of salt and do your own research (kinda like this)
https://rvlifemag.com/cracked-battery/