Makes sense for T6 to be slower with the smaller beam for example.From what I heard the original expectations inside the INEOS camp was for T6 to be significantly slower than the AC40s.
I can understand having T6 in full 'mule' mode with easy access for mods etc but it does seem odd that they won't be able to run a boat-on-boat training programme.
2 boat tuning makes sense for practising starts and fine tuning a race boat, but that's not what T6 is for. For this stage the 2nd boat is the simulation. If they change X, does that make the difference the sim suggests. If so they can use the SIM to design the race boat, if so they recalibrate that part of the SIM.
This is even more the case with dynamic areas such as ability to lift out and turns where it is almost impossible to duplicate what the 2 boats are doing (whether it be trim changes or waves at that exact movement) so you don't know know what causes any differences. yes you can repeat to eliminate random events to some extent, but again, easier to do against Sim