Putting my bass players' hat back on...are we just more aware of our EQ, and the way it affects the way our tone sits in the mix? I wonder if the fact that we have to achieve "presence" in the mix, in the face of more limited audibility, is the reason that bass amps are much more likely to have a graphic EQ built in than guitar amps are! I've certainly played with a few guitarists who didn't realise that cranking their amp's bass control might have sounded great in their bedroom, but just coated a band mix in sonic wool.
And in the interests of balance, there are still bass players who think that active pickups and onboard EQ are the devil's work, and will only consider passive basses. (Almost me: I only own one active bass to ten passives!)
I hadn't heard of those before, but I'm very intrigued! Speaking on direct substitutions, I did stumble across the "warm stone" developed by AMT: https://amtelectronics.com/new/amt-12ax7ws/
Not sure how they compare to "the real thing," but whilst I've been quite lucky with valve amps so far, I would be happy to consider a more reliable alternative if it sounded as good!