I assume you're talking about iOS apps here. If so, I don't believe there's a way you can do that. The 17+ labeling comes from Apple, so you have no control over that. The restriction of 17+ apps setting simply uses the ratings Apple applies to the apps to determine if they are allowable or not.
If I'm not mistaken, this has been an issue others have run into. Basically, any app in the App Store that has either a built in browser, or is a browser that can load unrestricted or unfiltered WWW content gets labeled as 17+ since its possible to access "adult" content with it. So Chrome and YouTube fall under that category, and I don't think you can bypass that. That being said, I don't manage any iOS devices with the Casper Suite right now, so take what I'm saying with a grain of salt. Maybe someone else who does manage them will confirm (or deny) what I'm saying.
You'll likely need to bring it up with Apple, and not JAMF since its Apple labeling and Apple's MDM we're talking about. I would agree that it may be a bit too 'black and white' how it works now. More granularity over what can/should be blocked would be nice, but again, JAMF can't provide it if Apple doesn't allow for it.
One possible solution is to change the MDM methodology from a restricted software "blacklist" to an approved software "whitelist". Obviously, I do not know if this would work in your environment and workfow; still, take a look at this link if you have not already: https://jamfnation.jamfsoftware.com/featureRequest.html?id=1881