I've always thought that while BMI is crude, it still is reasonable for measuring metabolic syndrome, considering that many of the things associated with heart problems involve the needing a powerful heart, when adding any mass whatsoever will necessarily increase the work the heart must do.
It seems to me that in the usual case where a person develops muscle mass by working out, this isn't a problem because whatever "blood necessary to maintain excessive muscle" is negligible in the face of the body adapting to improve the cardiovascular system in order to serve muscular oxygen needs during workout. Of course, heart problems due to an unhealthy person ramping up exercise too quickly is a concern, but this is separate from your concern.
One also observes that athletes in general have lower heart rates than the average person; whatever additional burden their muscles impose, their cardiovascular system is way more adapted to handle that due to exercise.
Here are some things I found in a brief glance at google scholar. There appears to be a condition called Athlete's heart, but I dunno:
https://pubmed.ncbi.nlm.nih.gov/26187713/
https://www.degruyter.com/document/doi/10.1515/jom-2020-0046...
The second describes the same thing:
> Several middle-aged and older men trying to improve their physical fitness by weightlifting have presented for repair of severe mitral regurgitation, some of whom stated that they remembered feeling a pop in the chest while weightlifting, which was the start of their dyspnea.
> Arterial BP increases most during weightlifting that is accompanied by mechanical compression of blood vessels (such as when bent forward at the waist or squatting) and when accompanied by a Valsalva maneuver.
Neither of these papers link them to muscle mass but to the stress of high-intensity exercise itself, which I have already addressed.
I agree that we should not assume things, but in the lack of cursory evidence, I would still stand by my argument that in the normal case where muscle mass is formed from working out, such workout stresses and modifies the cardiovascular system to such an extent the result is a body that is more than capable of handling whatever stress that muscle at rest imposes on the heart.
Once again I reiterate my cursory evidence to my argument, that athletes' cardiovascular system are generally so much more efficient and less taxed than the general population that their hearts beat at 3/4 the average heart rate.
It seems like athlete's heart syndrome is a benign condition.
Overall, I think BMI looks like a pretty useful metric considering how easy it is to measure. That would explain why it sticks around despite being frequently criticized.
See charts 2.A and 2.B in: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2877506/