I'd go out on a limb and say that it's McDonalds corporate that doesn't trust the franchise owner with the machine, not the manufacturer trying to swindle franchise owners.
The question remains - what's the barrier to entry to becoming "certified" as an ice cream machine cleaner?
Is it legitimately a difficult cleaning process that requires an extremely specialized skill-set that only the High Priests of Ice Cream Machinery are able to perform?
Or, as seems likely to me, cleaning the machine is relatively simple, but the ability to reset the "time since last cleaning" setting may be artificially restricted?
If I were the manufacturer of these Taylor ice cream machines, setting them up with a "one of our certified technicians needs to touch them at least once every 14 days, or they stop working" seems like an excellent way to seek rent / generate passive income.
It's "artificially restricted" in the same way that I could give anyone a key to my house (duplication is trivial) very easily but I don't.
Suggesting the franchise owner do it or even the store manager is far off from how these operations work in my experience.
Franchisees (Owners) have so much to do. They never "have" to work a single shift after they complete onboarding. While this can take around 9-12 months once most are done they never look back. Owners are tasked with running and growing the business, focusing on their local community and the people element. Any equipment work is not considered a good use of their time.