I can confirm this, pressing [RMB] makes the gun rise, but the view (zoom) doesn't changes at all, making the scope all but useless. It is still possible to zoom in and out with the [NUM+] and [NUM-] keys (at least for me), but it should zoom in automatically like with every other gun and scope.

I regognized it with the M4 and a red dot scope. I pressed RMB and gun was rised up but no zoom. Then I pressed RMB again and hold it-> Scope zoomed in. I dont think that this is a bug.

Then why do all the other weapons, scopes and sights doesn't work that way? Including the M68 sight, which is basically the same red dot sight as this one.

Did you try it with one time RMB, then press again and hold it?
I only tried the other red dot scope (blue one).

[M4 with T3 RDS sight]
M4 in lowered mode
click [RMB] once
brings up gun, same zoom as without gun, can zoom in with [NUM+] and by holding [RMB]

[M4 with any other sight]
M4 in lowered mode
click [RMB] once
brings up gun, zooms in to the max zoom level of the RDS automatically

[any other gun]
gun in lowered mode
brings up gun, zooms in to the max zoom, except in LRS, which can be zoomed further in, cause LRS is like that

So, yes it zooms in by holding the [RMB] or the [NUM+], but this isn't the way it supposed to be and zooming it manually each-and-every-time-you-want-to-look-at-something-you-saw-over-there is quite annoying. Wish I could post pictures when the issue is clear, but I'm currently at work.

Thanks for the details.
I like the fact, that there are two different types of handling the red dot scopes. So if you got both scopes (T3 RDS sight, M68) you can choose. The new method is good for CQB, cause you dont zoom in that much and you can also see the action around you.
It would be nice if you add screenshots. Happy working :-)

I've added some screenshots where you can clearly see that the T3 RDS sight doesn't have the same amount of zoom as e.g. the revolver, and also that the M4 zooms better without a sight than with this sight.