Maxon ported ZBrush to iPad (released last year) https://www.maxon.net/en/zbrush-for-ipad

I'm not sure exactly what that means, intuitively I agree with your comment, but I guess the ZBrush port acts as a data point that's at least a partial counterargument (only partial because, e.g., Maxon hasn't ported Cinema 4D, which is more directly analogous to Blender).

I'm really curious about the ZBrush port, e.g., is that really because customers were asking for it (or usage data from Maxon's own iPad-only [acquired] app Forger indicated there was interest)? Or is it a defensive move trying prevent an Innovator's Dilemma-style disruption from the bottom from an app like Nomad Sculpt https://nomadsculpt.com?