There is no inherent problem -- the suggestion is there to deter people who
don't really know what they're doing from trying it, screwing up their
MacOS partition, not having backups, and then screaming about it.
Flailing away on a separate drive's partition map reduces your chances
of destroying some data that's dear to you, that's all. If all you've
got is one drive, you've got backups, and you're comfortable taking
the risk, go for it. Lots of people have done it.