Outside collaborator requires a seat for each project?

We are using a paid-for github. We have outside collaborators for multiple repos. I was able to add them to the 1st repo just fine, although we did need to buy one more seat. Now i want to add that same list of collaborators to 4 other repos, but when i try to invite them i just get this error:

You must purchase at least one more seat to invite this user as a collaborator.

Is there really a requirement that the same users cant have access to multiple repos or is there a different way I can give them access to the other repos.

thanks

Hey! You will need to add the outside collaborator to a team and give the team permission to see the correct repos you want.

with our scenario, we dont want to give make the external people team members (mostly for security purposes), we just want to give them access to specific repos. or maybe setting up a team with only rights to that one repo is still as secure?