"Relationship type" empty for half of all relationships with symetrical names

Steps to reproduce:

1. Find a relationship type in which the values "Relationship A to B" and "Relationship B to A" are identical, e.g. "Spouse of".
2. Create an individual conact (eg.., named Bob) and another one (e.g., named Alice).
3. Create a relationship of the type "Spouse of" between Bob and Alice.
4. Navigate to Bob's "Relationships" tab, and click "edit" for the relationship to Alice. This opens the relationship edit form. Observe the default value of the "Relationship Type" field.
5. Navigate to Alice's "Relationships" tab, and click "edit" for the relationship to Bob. This opens the relationship edit form. Observe the default value of the "Relationship Type" field.

Expected vs actual behavior:
In the last two steps above, the Relationship Type field should say "Spouse of", but for one of those steps (either Bob or Alice), the Relationship Type field will have no selected value.

Bonus steps:

1. Edit the "Spouse of" relationship type so that the values "Relationship A to B" and "Relationship B to A" are different, e.g. "Spouse of (a)" and "Spouse of (b)".
2. Repeat the last two steps under "Steps to reproduce" and observe the expected behavior: in both cases, the "Relationship Type" field has the correct value selected.

Miscellaneous:
I'm wondering if perhaps this is related to CRM-9347.