That’s not written or inferred anywhere
On the contrary, the AR Mk1 (and possibly A4) OS is being held up due to its tie-in to the upcoming OB release - so that Mk1 is running on OB2 (yet is not listed)
This does not imply that the Mk1 will be as feature complete bandwidth wise as the Mk2, the AR mk2 will be able to handle more simultaneous channels than the Mk1 - the same applies to the A4Mk1 wrt the Mk2, however, it’s not entirely clear whether the AK will be an exception here as its USB circuit (the same as A4/R mk1) may be better isolated on a bigger PCB and may offer a better bandwidth if this is the case
All the Mk1s have USB2 hardware but we’re forced to run at equivalent USB1.1 speed due to noise issues - perhaps the AK is better in this regard, but I suspect the list on the website is targeting currently available products … if you’re ‘selling’ OB, you’d want to tie it in to current products on sale - but I expect all OB capable devices will run on OB2, some better than others, whether the AK will be better than an A4 Mk1 is anyone’s guess