It is probably a BIOS issue. Some show other partitions as boot options even if they are not UEFI bootable.
When you say 'When I ask to display my UEFI Boot menu,' what exactly do you mean? Are you pressing F12 on boot for BIOS Boot Selection menu pop-up?
Make/Model/BIOS rev.?
In WIndows\Linux OS, can you Change option to show all files and hidden files in File Explorer and then give us details of Ptn 3.
FAT32/NTFS/exFAT? Size? How made? What files and folders are on it? Partition Type number of ptn 3 (RMPrepUSB - Drive Info - 0)?
Any hidden folders?
When you say 'When I ask to display my UEFI Boot menu,' what exactly do you mean? Are you pressing F12 on boot for BIOS Boot Selection menu pop-up?
Make/Model/BIOS rev.?
In WIndows\Linux OS, can you Change option to show all files and hidden files in File Explorer and then give us details of Ptn 3.
FAT32/NTFS/exFAT? Size? How made? What files and folders are on it? Partition Type number of ptn 3 (RMPrepUSB - Drive Info - 0)?
Any hidden folders?