Not quite, in theory the converstion to an XJ6 rack has two issues:
It causes bump steer
It affects that ackerman angle.
In practice I found that it drove fine, it might scrub a bit more on tight turns when parking but this is hardly noticable.
Most people on Jaguar Forums who go on about the problems with this conversion have never driven one with it and just latch onto the theoritcal technical issues and the legend goes on and on.