It is rather confusing, I agree. Not helped by there being two or three closely related topics covered in different places with a degree of overlap.
The one you link to is valid, only don't think of the "Really busy" section as being worse than it says. For example, the Olympics went through without a hitch and a lot of capacity has been added since then. But if one of the major Plusnet links went down there is a backup plan as described there, and if North Korea chuck a nuclear missile at someone every ISP would be under huge pressure.
The prime link for actual throttling, which used to have rather forbidding tables in every drop-down, not just a bit in a few, is
this one. With
this very informative blog which explains the effect of the priority levels you just linked to

. Make sure you read, rather than skip over, the sentence immediately under the picture.
My broadband basic info/help site - www.robertos.me.uk |
Domains,website and mail hosting - Tsohost.
Connection - Plusnet UnLim Fibre (FTTC). Sync ~ 54.0/14.9Mbps @ 600m. -
BQM
"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.
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Allergy information: This post was manufactured in an environment where nuts are present. It may include traces of understatement, litotes and humour.