Coordination of 403(b) and 401(k) Plans

I apologize in advance if the question is not formulated clear enough.  I am trying to establish the framework to analyze the coordination of multiple employers, so the high level summary and IRC sites/links will be appreciated as well as reference to educational materials not in violation of proprietary information policies.

Let's assume we have one person who works for an organization sponsoring 403(b) plan making in excess of $330,000 (just to avoid the math) as a W-2 employee. The person is under of 50. The same person also owns a single member LLC taxed as a sole-proprietorship that sponsors a "solo 401(k)" plan.  Let's assume there is no CB/DB plan in a picture for time being.

Scenario 1 - The organization is a non-profit hospital.  Then the 403(b) plan is deemed to be controlled by that individual.  The individual also has his own medical practice (no common law employees). Therefore, the maximum benefit will be $22,500 in 403(b) deferral and $43,500 in PS allocation in solo401(k).  Both 403(b) and solo 401(k) are integrated for purposes of 415.  Do you agree?

Scenario 2 - everything is the same as above but the business is NOT a medical practice.  Let's say it is a medical technician type of activity.  Does the answer change?

Scenario 3 - the organization is NOT a non-profit hospital but rather the educational institution (University of State for example).  Does the answer change?

I am looking to understand the general framework when the non-profit 403(b) MUST be aggregated with the individual 401(k) and what are the exception to that exception of "separate employers" rule.  I think there are some exceptions to exception and that is where it gets very muddy for me.  Help and education are appreciated as always.

For reference, here is the IRS snapshot on this issue: https://www.irs.gov/retirement-plans/issue-snapshot-403b-plan-application-of-irc-section-415c-when-a-403b-plan-is-aggregated-with-a-section-401a-defined-contribution-plan

I don't see any special exemptions for the type of 403(b) sponsor (educational, medical, governmental or otherwise) or for the nature of the other business carried on by the participant. If a 403(b) participant owns or is deemed to own another business, and that business sponsors a 401(a) qualified plan, the 403(b) plan and the 401(a) plan are aggregated for purposes of 415.

Thank you C.B. Zeller.  I thought (and it might be the imagination) that if the 403(b) is structured as a church plan, there is an exception to exception?

That may be. The snapshot linked above contains a reference to IRC 414(c)(2) which discusses aggregation of church plans. It's not something I have any expertise in.

Agree with CBZ, as we had that exact situation with a university employee who was also a business owner and ended up doing a DBP because of the DC aggregation. I have no thoughts on the church plan side of the discussion.

the actual source of the rule is Treas. Reg. 1.415(f)-1(f)(3).