Currently there is no way to ignore any request.
One option is to separate the auth step out and use Feeders: https://github.com/intuit/karate/tree/develop/karate-gatling#feeders
If you refer the Gatling docs: https://gatling.io/docs/current/general/assertions/#scope – it may be possible to “scope” the percentile assertions to a group or name.
Here is someone who seems to have had success with a custom Group name: https://github.com/intuit/karate/issues/858#issuecomment-546410352
To be honest, I don’t think there are many Karate users using percentile assertions. Can you confirm if any solution works for you, it will help others. Also do consider contributing, I’ve added your ask to the roadmap: https://github.com/intuit/karate/projects/3#card-22529251