Well, first, to repeat perhaps too many times, I can't speak for MP and their warranty policies.
But, the LP is not really designed to handle a tube which, IIRC, has an op point so far from 6922. My guess is that if the LP could bring itself to a proper operating point (meaning basically 0VDC at the output), the amp would be stressed to do this.
Keep in mind that the internals are set to reach a "design center" operating condition and they are designed to handle reasonable variances around the design center for variations in 6922s. The full range of the LP can handle larger variations than this, but this leads to more power dissipation and higher stress on some of the components. So while it can bring wider variations into center it doesn't expect to stay there and only expects to see those conditions during start up while it is zeroing out the DC and settling everything else.
MHO is that there is risk to do this roll that may not appear immediately.