Could this fit be a coincidence? I don't think so! Someone in industrial engineering at M&M-Mars must be a medium format film nut! So how long has anyone been using these? Do the lid hinges break over time? I would think they should, since they're meant for single use (or at most, maybe a handful of opens & closes if you don't eat the M&Ms gluttonously in one sitting). Not that it matters; a film in one of these cans even with a wobbly top is still safer than a film loose in the camera bag.
I remain perplexed as to how the film world reached as its norm this daft situation where 135 films, safe in their cartridges and not needing much protection, are sold with canisters; while 120 films, which need a lot of help to avoid light contamination, typically are sold without. Kudos to Adox for having helpfully bucked this naked-120 trend, and for using stickers that come straight off (no hot water needed), making canister reuse easy.