I agree with you there probably should be mixture of wrappers, I’ve also said the taxation bit isn’t wrong either, but what I’m very sure about, is that people shouldn’t read your post & take it as guide to their taxation needs.
Individual circumstances mean there’s different options for different income at certain ages. For instance, I hope to sell a business when I retire, that’ll be taxed at 10% entrepreneurs relief. Hypothetically, I might never need to draw on my pension. Let’s just say I’ve put £400k into my pension, £500k is actually there. I die before 75, my family get £500k tax free, as opposed to the £400k in the ISA. That’s ignoring IHT issues, which we’d all be in a lucky position for it to be a problem.
As I said, info you provided isn’t incorrect, but it’s dangerous for anyone to take it & apply it to their own circumstances. Everyone needs a plan reflecting their circumstances.