dedupe rule fails with event registration if email not used

this is an interesting one. here's the setup:

1. create your individual unsupervised rule to be first name and last name, with weights/threshold such that both field matches are required (i.e. each weight = 1, threshold = 2)

2. create a profile with first name, last name, email

3. if you use that profile in create mode multiple times with the same name but different email addresses, it will correctly match the contact and update the email address.

4. but if you use that same profile in an event and register someone who exists in the db, matching the first name, last name, but not email – it will create a new contact.

5. if you repeat step 4 and do match the email address, it will match the contact.

I haven't traced it through yet, but it appears that in the context of an event, a match on email is being strictly required, regardless of how the unsupervised dedupe rule is constructed.