Honda spends 2021 only running the spec that is frozen for that year? That wouldn't make sense, their Super GT engine uses a similar combustion process minus E-turbo. I believe Honda will continue developing until the end of 2021 with the aim of the following year, only reason why Red Bull would take over the power unit for 2022. If Honda is leaving them with a competitive power unit for 2022, then with left overs from the budge cap and the fact that in season development is essentially frozen, Red Bull could run and develop certain aspects of the power unit through 2022. This is of course assuming the power units will be frozen entirely by 2023. Or if any development does happen it would be a pooled development for a standardized part. That the manufacturers agree to develop a specific part of the power unit, that part becomes a standardized part usable by all manufacturers and the cost of R&D and manufacturing, and testing, and implementing that part becomes a pooled and distributed investment. The IP for said part can be leveraged by all teams if for example said part is made by a common supplier, for example fuel injectors. Piston wrist pins, or crank or rod bearings.
If a team doesn't want others using certain components then they are forbidden from being upgraded or changed. If they do, then others get to learn what they want to upgrade, and the part can only be upgraded if other manufacturers agree, then all manufacturers pool their resources to develop said part, and reap the benefits. That way power units still develop but in a much more controlled fashion. It will stop teams from making large scale changes to the power unit, as not all components may contribute to the performance of each manufacturer in the same way. This will make teams reluctant to agree to any change to things that make their power unit unique, but will stop them from developing their unique component to the point of giving them an unfair advantage.
The height of cultivation is really nothing special. It is merely simplicity; the ability to express the utmost with the minimum. Mr.Lee