There are three chips we should talk about to clarify this:
i7-3632QM (listed by Nitrokey, not compatible with Qubes OS)
i7-3740QM (the one I used, NOT listed by Nitrokey)
i7-3840QM (listed by Nitrokey)
The i7-3632QM is that fastest 4 core 35 watt chip Intel makes and the socket 2 version of it, which you would need for the T430 does not have Vt-d. Although there is a i7-3632QM version that has it, but that one can't be used with the T430.
I originally ordered a i7-3632QM because I wanted to stay within the 35 watt design of the T430 and then found out that it lacks Vt-d when I tried to install Qubes OS. I asked Nitrokey about it and they continued to tell me that their i7-3632QM would have Vt-d. Then @Plexus made a post on the Qubes OS Forum regarding this and alerted the Qubes OS Team and that's when Nitrokey added the warning you saw.
You can however also use 45 watt chips with the T430 if you mod the cooling (like I've done). In that case the fastest chip is the i7-3840QM as offered by Nitrokey.
The one I've used is the i7-3740QM which was recommended by @Plexus. It's a tiny bit less powerful than the i7-3840QM but about half the price (if you shop right and not just go for the first listing on Amazon as I did).
Bottom-line: the i7-3740QM has Vt-d and works perfectly with Qubes OS!