That's (4) I think -- extending benefits, rather than being needed to get your vacation time. It falls into where I said "you're better off going on vacation, and then handing in notice". Handing in notice pre-vacation gives them the opportunity to say "well you're resigning anyway so today is your last day" in many jurisdictions, or simply inviting pettiness: a boss just refuses to approve your vacation request after you hand in notice - it doesn't save them money to refuse it, it's just being petty.

The whole point of the article is that you benefit from giving lots of notice, but that's just not true. Say you want to quit in 8 weeks, you could give 8 weeks notice today, or you could give 2 weeks notice in 6 weeks. In both cases you get employee benefits for the same amount of time, you have the same opportunity to use vacation time, etc. But in the former case you also have the option in many places for them to just say "ok, today is your last day" - I _think_ in less anti-worker areas such a dismissal would not be valid (e.g. the company can stop you entering the premises, but would have to consider you still employed, _or_ they would have to report you as being terminated rather than resigning which has legal implications for them), but even then you aren't getting any real benefit from the early notice.

Honestly the only people who gain anything from you giving advanced notice is your employer, and these are the same employers who can (and do) fire you essentially without notice.