If I recall correctly, the stick sometimes will displace other disk drives in the numbering sequence. So its presence/absence would affect the accuracy of the grub menu on disk drives?
Are you trying to boot an internal installation from a USB stick? If not, then there can be no conflict. You are booting whatever is on the stick.
Mounting is now done by partition
UUID number or
LABEL, so designation by
/dev/<whatever> is not involved.