One tax season later, I figured out what the issue was. Posting an update here in case someone else hits this.
(The 2023 edition has the same bug still, but I now know how to work around it!)
When entering partner information, I cut and pasted the EIN of the partner. However, TurboTax pasted the EIN in the SSN format. EIN has one hyphen, SSN has two. This tripped up the checker to think that the PR is a person, while the PR was in fact a company.
The solution is to go all the way back to entering the partnership information, and editing the "SSN" field of the company which is a designated partnership representative (PR) to be formatted as an EIN (XX-YYYYYY), not (XXX-YY-ZZZZ).
