It's more of seeking for additional profit. Altcoin season usually happens once bitcoin is having a big rally. To maximize profit at time like this you need to rotate your profit from bitcoin to altcoin before it's going up.
It could be true to some extent but just because altcoin season happens in previous cycle doesn't mean it will happen right after bitcoin bullrun again.
More of a bet in my opinion where you're betting the bitcoin dominance to dump so sharp and altcoin price increase.
You can only maximize profit using this method if you can have a perfect timing for your buy and sell the right altcoin.
Not altcoin behaves the same with Bitcoin so you might buying a shticoin that doesn’t move or rally greater percentage than holding Bitcoin growth itself.
The best time to sell Bitcoin is when it reach new ATH and do it in tranches.