So the jumper in the W2 and W3 are for when that mount kit is used to surface mount an AP, but there's no port or cable behind the mount and the cable has to come in from the side. You use the jumper and the snap-in coupleler and knock out one of the knockouts for the coupler to snap in to.
For the 205H, that jumper would ONLY be needed when you are blocking access to the back of the AP and want to redirect the back port to the passthrough into the bottom (like when you use the deskmount kit which blocks all access to the back of the AP). So if you buy the deskmount kit, you will get the small jumper. The umper in the mount is designed only to bridge the two connectors on the back for the passthrough port.
I'm curious why you need the jumper on the 205H without the deskmount kit? if you are wall mounting the 205H, the port in the back is already accessible. So in your OP, it sounds like you are dealing with tight tolerance to connect the keystone ports in your 1gang box to the 205H, but that is not every customer install as most will pull the terminated RJ45 into the box, or will use a biscuit in the plenum and jumper a longer cable from the biscuit box into the 1gang box the AP mounts to. So while you need it, it's not likely all our other customers will, and as you know, they go with the minimum.
So for the deskmount, because the mount itself physically blocks access to the back port, that jumper cable is included. For the W2/W3, there is a F-to-M jumper to cover when the W2/W3 is solid wall mounted and the ethernet cannot come from behind the mout (ala thorugh a ceiling) and the cable has to come from/down the wall outside the mount. For all other installs, say to a 1gang/2gang electrical box, it's assumed that there is an RJ45 connector in the box (as that is the vast majority of installs), not a blank/empty keystone jack that would require a MtoM jumper. And outside of that, 6in jumpers are easily acquired. Finding smaller ones are a bit tougher yes.