He is 100% accurate. Only 100k per month is the problem. It’s what leads your base to be weak (due to no hut eggs), it makes you level slower and you hold back your timers because of this (why you “hoard” timers). It makes you score less in each event, which earns you less sigils per event, which then makes you earn leas rewards per season, which lowers your progress.
This game is more of a snowball effect. If you do well in an event, it propogates. You do well in the event, you get more sigils. More sigils and you get more prizes. More prizes means doing even better the next event, which gives you even more sigils the next event, etc.
If you start to limit yourself to 200 or 250 sigil prize per event and save 100% of your rubies, you are really really really hurting your overall progress in the game, seasons and overall not playing very effectively.
(Yes I know going overboard isn’t good either, rewards are less efficient at higher progress levels. A balance is required)