Can a rebias alter the sound of the tubes?

I sent my Sonic Frontiers Line 1 back to the factory recently for a 'SE' upgrade. Rather than 'upgrade' to their current choice of tubes I sent along my carefully-chosen nearly-new set of Tungsrams and Electro-Harmonix and asked them to rebias the preamp to these tubes. Which they apparently did.

This tube combo gave a wonderful weight and holography to the sound, subtle but noticeable. Now it's gone. Careful A/Bing with a good solid-state pre I also own I can hear no difference in the sound. While this may not be a bad thing, it renders all the time, expense and results of tube rolling moot, and removes the sonic attributes of tubes, despite SFI gear sounding non-tubey by design. The improvement from the handful of upgraded SE components doesn't play into what I'm hearing here.

So can rebiasing of any tubed pre alter the sonics of the particular tubes? Would the factory bias settings return any tube to the neutral SFI 'house sound'? And if so how do I get back to the sound I once enjoyed? It seems wrong to intentionally set the bias off to get 'better' sound. I don't know the biasing procedure for the unit (yet), and I sure don't want to adjust my way into a black hole. What would Chris Johnson do? Or any other knowledgeable tube-heads?