A few good points in the article, but some of it is outdated/UK specific.
In terms of checkout, there is no need, (at least domestically,) to check out in person. Regardless of whether you are mattress running or not, in person checkout is no longer necessary, and hotels prefer you skip it.
You do not need to be careful on a multiple night stay about housekeeping noticing the remade beds weren't touched as most hotels post covid will honor your request to not have housekeeping enter the room.
The point about someone else checking in for you is important. I recently witnessed a couple where the woman was the second name on someone else's reservation. When it became clear that the named WOH member wasn't present (they asked for a credit card in his name) they asked her if she wanted to add her WOH number as they had to remove the member who wasn't present.