sounds correct, they are all just an earth loop to the speedo and when 1 gets cut by the disk it breaks the earth and the warning lamp comes on.
You replace both sides when your pads are worn so it's kind of pointless having both sides, if you don't have the loop then you can make 1 from an old sensor wire by cutting an inch away from the plug and joining the wires then sealing them.
If your old sensors are in good condition, you can reuse them, i find that the plastic bit which goes into the pad tends to become brittle and breaks when you remove it

Some aftermarket sellers sell both and some give you none:-(
You could probably buy them separately from Ford.

Ps. If you wanted both sides in case the opposite side wore out first and scratching the disk then you might have a problem and your calipers etc want freeing up/servicing.
I tend to keep an eye on mine and Try not to wait until I'm touching cloth

56 350 2.2 130ps mk7 with 2 side doors
65 290 2.2 125ps custom with 2 side doors
07 350 170ps
Ids v86 licence + v86.04 update + xprog
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