Unfortunately this didn't really clear up my confusion. In particular, the points brought up by the second answer there seem relatively unresolved. Why should DO graduates be growing significantly faster in number (proportionately) than MD graduates, when traditionally an MD degree is more desirable than a DO degree, despite both being mostly equivalent?
A few possible conclusions. I don't have enough knowledge to pick one. Some of my speculation might even be wrong.
(A) DOs and MDs filter through different or mostly different residency pipelines. Thus, residency limits for MDs don't affect DOs, so the DO population can grow more quickly.
(B) DOs and MDs do filter through mostly the same residency pipeline, and the increasing number of DO graduates is causing an increasing number of residency applicants to not be admitted to any residency program. (This malicious situation would be similar to the situation with law schools, which admit and graduate far more lawyers than the industry can possibly sustain and support in its current state.)
(C) There's enough non-government funding of residency slots that residencies are not as bottlenecked as the first answer claims. If so, this re-raises the question on whether MD admission is being rate-limited to increase scarcity and thus salaries.
A few possible conclusions. I don't have enough knowledge to pick one. Some of my speculation might even be wrong.
(A) DOs and MDs filter through different or mostly different residency pipelines. Thus, residency limits for MDs don't affect DOs, so the DO population can grow more quickly.
(B) DOs and MDs do filter through mostly the same residency pipeline, and the increasing number of DO graduates is causing an increasing number of residency applicants to not be admitted to any residency program. (This malicious situation would be similar to the situation with law schools, which admit and graduate far more lawyers than the industry can possibly sustain and support in its current state.)
(C) There's enough non-government funding of residency slots that residencies are not as bottlenecked as the first answer claims. If so, this re-raises the question on whether MD admission is being rate-limited to increase scarcity and thus salaries.
(D) Perhaps something else I'm not thinking of.