Gibson has done many many iterations of the single and double cut junior over the years. The current single cut has a 50’s style neck, but the current double cut has a 60’s style neck. The double cut plays very similar to the single, but at least to my ears, they don’t have as much tone as the single cuts. You can search back to the 2001-2012 year runs of the single cut that had a 60’s neck, but they’re pretty different guitars compared to the one you played from the modern era. They didn’t have the body shelf like the 50’s and current juniors had, and they also had the lightning wrap around bridge.
I’ve had juniors from just about every run from the USA line to CS and even vintage. I agree the current neck on the 50’s Junior is uncomfortable, but that’s because the flatten the back of the neck too much, leaving uncomfortable shoulders on the neck. The current CS junior necks are more comfortable to play and very r9 like. Round c shape but not huge. My 55’ has the second thinnest neck on any junior I’ve owned, the thinnest being the first run BJA Junior from 06-11’. An earlier 2006-2008 BJA would be closest in specs to the one you played at GC, has the shelf and the original angled bridge studs, but has a very slim 60’s style neck.