Your 5000 used firmware in the same .exe format as many other contemporary nuvis of the day, but the contents are different as you've found. Up to version 4.10 was supplied as only an *.exe file which can be extracted with winrar or similar de-compressor to then find B074300.update in Nuvi5000_410/Nuvi5000/Garmin/Updater. However RGN_Tool will not open B074300.update even if the file extension is changed to .rgn or .gcd.
With V4.10, it was supplied also as an rgn file, named Nuvi5000_regionfileonly__410.rgn and that can be opened with RGN_Tool but doesn't obtain a boot.bin.
I'm unable to say whether 5000 can have region 41 dumped because of the way this firmware is compiled. Certainly other conventional OS models of that time such as 2x0, 3x0, 6x0 could not have 41 dumped to SD anyway even though they had conventional boot.bin in their fw.
nuvi5000 V4.10.rgn file can be downloaded from the Perry site:
Using RGN_Tool to obtain a boot.bin proves problematic because it only displays 'virtual_image.bin' in first section where 'boot.bin' would normally be and no other sections are populated. virtual_image.bin is 69,754,880 bytes [~66.5 MiB] which comprises all of the firmware.
Please Login or Register to see the links
Maybe one of the Navigation Software Experts can explain further.