Whenever bitcoin price is not changing or changing very little, it is the best time for the shitcoins to be pumped as a matter of fact! But if bitcoin price is going through a significant change (rise or fall) the altcoins usually dump.
The reason is pretty simple actually. People who trade bitcoin, usually trade altcoins as well. And traders need volatility to make profit. So when bitcoin price is not changing, they cannot make any profit either. So they start moving their coins/capital to the altcoin market to be able to make some profit there while bitcoin is stagnant. Consequently this increased liquidity helps pump shitcoins.
Exactly this is what the whole altcoin season is about, altcoin season happens only when the bitcoin dominance reduces, this has been long misunderstood by many thinking that bitcoin must actually dip before it happens but it is not just like you have said it is when the market has pumped and begins consolidation that the altcoin season begins because funds are moved there. If bitcoin dips every investor will be scared and no one will be going to gamble their money on shitcoins. But right now I don’t think Altcoin season is upon us or even coming anytime soon because this current trend of the market wouldn’t allow any one to actually go buy shit tokens when the market is still not stable with fears of economical wars and others still lurking around