You can call it what you want, but for what I (and others presumably) use it for, the 24/7 uptime is essential. Sure an argument can be made for needing to pay for 24/7 uptime, but it is very clearly a downgrade in such a case where such an argument even needs to be made!
To clarify: I'm particularly speaking about the parent's use of the term "sidegrade." I'm not disagreeing with the idea that 24/7 uptime should be paid for (because I agree), but to call the change in terms of service a "sidegrade" is a misrepresentation of what it actually is: a downgrade in services for my particular use case.
You can have a web dyno and a worker dyno running side-by-side 18h/day for free in the new free tier (unless I've misunderstood something.) You can't have one web worker running 24h/day for free, not as of next January.
18+18 > 24
I understand that your (and my) particular use case are affected negatively by this, but if it wasn't totally clear what he means by sidegrade, that's about the size it. More compute hours for your $0, but less availability.