I think you're misrepresenting their reasoning.
Screeps Inc thinks they can serve the communities desire for a flavored seasonal server better than ScreepsPlus can. They've been reluctant to try before now because of the effort involved. An official clone of the ScreepsPlus seasonal server wouldn't really be worth it (and possibly risky optics). If they're going to compete with ScreepsPlus's seasonal server they need to make it better. They've defined better as resurrecting the World Review and adding seasonal flavors. They're checking with the community if they're OK with this. Would you pay for a better version of ScreepsPlus's season server?
They've been very consistent in their view on the CPU subs. You buy screeps to get access to the client which gives you access to private servers. If the community 3d clients every stabilize you wouldn't even need to do that. The CPU sub is the player paying for time on the Screeps servers whether that MMO or whatever. However Screeps Arena pricing plays out we will not need another CPU sub.
I think this confusion is partially why they're considering a Screeps Seasonal product. To help everyone grok that we buy the games and server time separately.
ScreepsPlus doesn't do flavors. We totally could. Custom leader boards aren't that hard. We could launch a World Review on ScreepsPlus. But we haven't. Would you bump up ScreepsPlus's patreon a bit if AGS agreed to do these things?
I'd like Screeps to offer services that don't make sense for the entire community but would work at a premium tier. Nickel and Dimeing? Kinda, but kinda ala cart. I'd love an official Logging and Monitoring feature, but few others do.
I'd also hope that Screeps Seasonal would add deeper changes or custom API tweaks eventually. ScreepsPlus could alter constants, or crank up the invader rate, etc. But I'd love something like all Swamps are lava and damage creeps and structures. Or a new
FLY bodypart. These would be really hard to do well with mods on ScreepsPlus.