To be fair, the average time folks hold on to their Watches is certainly way longer than one year.
I kinda agree with both of these takes, but not completely.
The „more space for battery“ point seems very weak to me as Apple usually very early on defines a viable battery life target for a product and sticks to it, investing juice gains from processor shrinking etc. in additional tech/functions. The stated (and real life) battery life of the Watch hasn‘t changed since day one of the S0 and I don‘t think an additional 3-4 hours would make any difference in real life. And if you really need more juice, there is the Ultra now.
The „nicer mechanics“ point is also not very convincing IMO. If Apple deemed the current band channel ugly/complicated, they wouldn‘t have designed the Watch like this in the first place. And I really don‘t think the spring system failed a lot IRL (like you already said).
OTOH, there is a reasonable amount of „smoke“ to all this, so there might be a fire. The only reason I see why Apple would actually do this would be if the bands get „smarter“ and basically become sensors that communicate with the Watch itself, thus enabling new (probably health-related) features.