If jekyll processes it I think it will remove any front matter - no way to stop it that I know of - so you need something else to maintain those files maybe? one way is you can tell jekyll to not nuke a folder in the _site directory though that is hard to manage other than locally - and even then prone to error.
You could have something else copy the files into the _site folder for - like gulp or npm, some sort of build process that could run after jekyll.
Your work around might be the simplest though.
Does the Ulta thing allow other delimiters besides the 3 dashes? I think some things allow other things like 3 ~'s?