Tube amps - what is auto bias?

I hope to get some advice from tube experts

I have a Bewitch KT88 amp with auto bias. Hence I don't need to adjust the bias manually.

My question: If I substitute the KT88 tubes with 6550, does it mean that the "auto bias" will be automatically adjust the bias to suit the 6550 tubes? A technician once told me that the bias for KT88 and 6550 might be different. Can all amps with KT88 also use 6550 without adjustments?

Thanks in advance.