In my honest opinion, it can be justified. Hypothetically lets say there's a super old KartZ map you wanted to port.Honestly, I just hope that I'm not breaking the rules just because of mods like are broken and have to be fixed by me or someone else. I just care to have a good time and if this helps with that, then I'm on board.
I do have an interesting question. Can someone port a pack that changes map or thing IDs to be better compatible with other packs? It's really small and something that can be fixed without modding the pack directly, but if mods were more plug-and-play then the game and mods would be more accessible for normies. It has been a while so I don't know if SRB2 or Kart have fixed the map ID problem, but I hope you see the point I'm getting across.
We have a community-maintained spreadsheet of all the Map IDs, and a lot of them are taken up. It's reasonable to want the port to work alongside a lot of the maps so we'd probably allow you to change the ID for compatibility sake.
It's also just an ID, changing it doesn't affect the experience or intent of the addon. If anything, allowing users to change it just allows for players to enjoy such ports alongside other addons with minimal risk or incompatibilities. Like the example of a photo being put into a new frame; it won't affect the actual product.