Your characterisation is broadly fair. The App Store's combination of race-to-the-bottom pricing, the removal of paid upgrade pricing (which Apple only partially restored in 2017 via "in-app purchases"), and the heavy promotion of subscriptions did largely kill the classic "pay once, upgrade optionally" shareware/boxed-software model for most developers.
The model Panic uses with Nova is sometimes called a
perpetual licence with a maintenance window, or more colloquially a
"buy once, updates for a year" model. You'll also see it described as:
- Timed updates / time-limited updates — you bought a perpetual licence, but free updates are bounded by a period
- Maintenance subscription — after the free window, continuing updates are framed as an optional maintenance fee rather than a mandatory subscription
- Hybrid perpetual/subscription model
There isn't one universally agreed-upon marketing name for it, which is part of why different companies describe it differently. The closest industry term is probably
"perpetual licence + optional maintenance", borrowed from the enterprise software world where this has been standard for decades (think JetBrains before they controversially went full subscription, or how many CAD and audio tools are sold).
The model has grown in popularity among indie Mac developers specifically as a response to user fatigue with pure subscriptions. Sketch uses a very similar approach, as does Setapp in a different way. It threads a needle that many users appreciate: you're never held hostage to a subscription to keep using what you paid for, but the developer still has a sustainable ongoing revenue stream from users who want to stay current.