Isn't this more or less what the Microsoft Long-Term Support (LTS) versus Short-Term Support (STS) is meant to do? LTS only receives critical updates but eschews all experimental/beta features. STS gets everything for the people that couldn't care less if their app gets hacked (e.g. apps like calculators, sandboxed internal tools, etc).

I know Ubuntu and others do the same but I don't know what they call their STS equivalent.

Depends which Microsoft products you're referring to. If you're talking about .NET versions, MS explicitly says "The only difference is the length of support."