You are right, and such disks will appear as empty to any tool or OS, but I will never insert any of my SSDs or HDDs that are used in this way in a computer that I do not control.
Windows frequently overwrites any bootable Linux drive, so it might have even less restraints with an apparently empty drive that does not have GPT structure.
Because of the risk of Windows messing with them, I also do not insert any of my bootable USB memories in a live Windows computer, even when they have GPT structure. For data interchange with Windows, I use only clean and non-bootable exFAT formatted USB memories.
I wouldn't recommend that. It makes the disk appear to be empty to many tools (and possibly some operating systems), which could lead to data loss. That's the reason GPT has the protective MBR: it makes the disk appear to be full to legacy tools which don't understand the GPT format.