TheCitrusDragon The type of crash, from the OS perspective, isn't usually helpful with this kind of problem. For example, in Windows, the saves-related issue throws a crash report that says Sims 4 crashed because Sims 4 crashed, and it was an access violation. An access violation is so generic an error—a program attempted to access memory in a way that is not permitted, so the OS shuts it down—that it can indicate anything from an in-game bug to conflicting software to a hardware issue.
What you've written sounds like the Mac equivalent of the above, which makes sense since the underlying problem with the saves is the same. "Bad access" is definitely the equivalent of an access violation, and most of the rest describes the memory address and the process that tried to access it and how it did so, and maybe a stack trace thrown in.
That doesn't mean crash reports are never helpful, only that they can't be relied on and are often misleading or far too generic to be of any use. The practical details are more useful: can the crash be reproduced, can it be stopped by performing a certain action (i.e. removing saves), that kind of thing.
By the way, we have a Mac Tech subforum too, for any future issues you may have:
The Sims 4 Technical Issues - Mac | EA Forums
The person answering most of the posts there is great with Macs and is always up to date on current issues with Sims 4, whether they're Mac-specific or not.