The changes we know about (reduced coach cost, increased weekly merch, increased lvl 2-3 merch store) are all things that have been discussed previously, and I believe most users would be in favour of these changes.
However if you bought a level 6 coach for $1m+ and then a few weeks later everyone else gets one for $700k because the game was suddenly altered, you might feel hard done by. Especially when the changes are secret and a small group are the only ones with knowledge of it.
I don't buy the explanation given:
I'd say the main reason why we didn't say anything was that we wanted to truly see if the prices getting lower when the supply is higher than usual.
I don't think the BB coach market is particularly special that you'd need to test whether increased supply reduces price.
Announcing about it would manipulate the staff market and the prices might not even drop because we would have more people than usual, looking for a trainer, simply because we said we put more trainers.
Yes that is possible. You could announce the change, ignore the results for a few weeks (it will be easy to track how long the artifical demand lasts), then when things settle down you can see the new "normal" results. A better alternative would be to announce it and slowly increase the supply over a longer period of time. It also doesn't explain why the other changes needed to be secret.
As I said above, I think these changes will be welcomed by the community. And my understanding is BB was stagnant for a long time so it's good to have progress being made. But in my opinion there should be more transparency. The exhaustion changes and league consolidation were good examples of that - they were introduced over a period of time (with more detail becoming available as appropriate) and everyone had the opportunity to be aware it was coming.