Oh, and as a reminder this is because I used an HTTP api gateway to 'forward' escrow's into the network our CryptServer is on, which doesn't allow the trailing slash and 'default' is the AWS... default naming of the stage we deployed.

I would prefer to not hard code specific implementation details for your environment. Is there any reason you cannot set your server url to what you need?

It's certainly not the communities problem that our infrastructure implementation is weird, but linux and windows 'agent' interfaces are using this same URL so migrating has more friction/requires more coordination for something as vital as FDE escrow. I'm honestly not sure if the other API gateway options (lambda-less and REST-ful) would even fix the incompatibility with trailing slash.
Currently (and historically, which is why we had been maintaining a fork,) the checkin script breaks our usage because it defaults to appending/ensuring the trailing slash url format - even if it may be considered more 'correct' (and admittedly is definitely a single standard that was always supported) it's not impossible another environment will ever want to support something like this.

A flag to not validate/enforce trailing slash would work for me just the same, should I add a pref or something instead?

I think the pref to not enforce the trailing slash makes sense