Interesting. If Magna adds bits that SR1 was missing, that seems to me that it's not like SR1. If it added more of what was already there, that's what I would personally call a continuation of the SR1. Like if I take a headphone that lacks bass and add a lot of bass, I wouldn't say it's a continuation of the original headphone, it's now different, it has what the previous lacks.
Just giving my $0.02 on why so many might see Immanis as the SR1 continuation. Also Immanis being the more spacious of the two, as you already alluded to.
I'm one of the people in the camp that Immanis seemed more in line with SR1 and Magna seemed more in line with CA-1a, to my ears. Not particularly in tone or FR, but in character, with Immanis being spacious like SR1 and Magna being punchy and dynamic like CA-1a.
You're right, I didn't express my concept of continuation correctly.
Also, it's important to know the actual scale.
What I understand as a continuation is when a new product adds improvements, but you can still recognize the origin of it. The quantity of things have changed, but the quality of them stayed the same.
The most important factor with any reproduction system is the tone balance of it.
The scale is the amount of difference in tone balance.
What I, and I guess everyone else, hears first is the tone balance of headphones. Timbre and space come later and it requires more time to assess, but the tone balance is understood very quickly.
Continuation:
SR1 is light/neutral balance, Magna is neutral and Immanis is warm/neutral.
CA1 doesn't resemble the rest in tone balance due to it's laid back presence region, which none of the others share with it.
The scale/qualitative difference:
It's not like that Magna has lots of bass. It adds to SR1 just the right amount to become neutral instead of light and it's the same type of bass behavior.
If you liked what SR1 does with bass, you will like the Magna, too, just getting more of the same kind of bass to get to neutral balance.
Immanis does not have exactly the same type of bass and it has a bit more of it, as a natural consequence of going from critical to slightly subcritical dampening.
That makes a different quality to it, besides the quantity, which is also slightly different.
In brief, continuation between SR1 and magna comes from using the same tools, getting same qualitative result, only adding the quantity of the result.
Immanis uses a little different tools, getting a different qualitative result and adds more quantity of it, to make a point. It is more of a derivative than continuation.