Those having issues are being mis-directed. This is a standard method for ordering service parts that are ordinarily not sold separately. For example, if you have lost a single AirPod, you can buy a single AirPod to replace it, through Apple Support, by ordering a service part.
I certainly believe the OP because this is how Apple has always operated for issues like these.
As to what you will receive when you place a service part order... it won't be in retail packaging, and it will either come in plain brown or a plain white box, with no accessories (e.g. no Lightning cable as you'd get buying a silver one).
Don't let them redirect you to sales, instead as them to treat it as though you had a faulty keyboard/trackpad/mouse, and to see what service part options are available to them.
Well when I asked service support for a replacement keyboard as mine is faulty. They said we can send the white version and make a note on system..so that whenever the space grey is available we will then look to replace that..so I don’t think the OP is correct.