Electrical – Help identifying this variation of a Molex or Amp connector please!

This is like a wiping contact without the wiping ;-).

When you insert an IC into a socket or plug in a USB plug and similar r=the primary action is metal sliding along a surface and coming into face to face contact. There will be some form of "spring" pressure to hold them in contact. Once gross oxide film is removed you usually get OK connections. Rub off all the oxide films and in many cases they would weld together.

In the case of the Magsafe connector it appears that the mating surfaces are Gold - probably Gold plus something to make it wear less. Gold does not form an oxide film (to iner) or perhaps rather, what film does form is extremely tenuous and almost wiped off by mechanical contact.

Old style Magsafe

New style Magsafe (broken)

Note that connectors that appear to mere mortals to work in exactly the same way (magnetic latch, surface contact, pull apart disconnect) have been used for many years on eg deep fryers for safety reasons.

BUT note that the page that you cited says

• Common complaints include plug separating from the cord, transformer shorting, and pin springs losing elasticity

Without spring pressure it will not make good contact.
With not enough spring pressure it makes not enough contact :-0.

As for how well they work - probably well enough but not as well as a properly designed connector.

"JST" is actually the name of a company that manufactures many types of connectors, and is not actually a connector type. What you have there is similar to a J.S.T. XH series connector.