The waiting 90 min for caffeine part is actually based on decent scientific evidence, but it's so damn hard.
Apparently the logic behind is that sleep neurotransmitters take a while to flush out in the morning, but drinking caffeine stops the flushing process and leaves you with leftover ones in your system. So as soon as the coffee wears off, you're way more likely to really crash.
I've tried to implement that habit, but ended up falling asleep at my work desk basically every day 🤷 (Although my doctor also says he's about 80% sure I have Narcolepsy, so that might have something to do with that)
It seems like a very common misconception that is maybe somewhat correlated, but causality hasn't been found as far as I could find. Probably one of those things that are hawked by "wellness influencers" and "hack your life" youtubers without actual evidence.