I have opened right now about a dozen Ghostty windows and about 20 tabs in each window, i.e. more than 100 shell instances.
I have started in as many of them as I could, before becoming too bored, a "ls -lR" on a file system with many millions of files.
I could not see any problem, much less any crash. I have been using Ghostty for a few months, very intensively, all day long, and I have not seen any crash or other suspicious behavior.
If you have seen a crash, perhaps there was either some specific version of Ghosstty that had a bug, or, more likely, some weird interaction with some other software that you have, and which might be buggy, e.g. the GPU driver. (I am using an NVIDIA GPU.)