When to buy first shoes?

My son is still wearing pram shoes as he’s only just started walking (he still crawls but walks a lot too now). I know it’s best not to put them in proper shoes right away and you should ideally wait 4-6 weeks.

My question is, should I wait 4-6 weeks after he’s fully walking and no longer crawling or 4 weeks from now when I’m sure he’ll be confidently walking?

TIA