I'd be interested to see a source for reload times on the Jagdpanther. From everything I've heard, the casemate was actually fairly roomy (in a relative sense) You would think the Jagdpanther would have a faster reload than the Tiger II, even if only a little better.
I agree. The only time I'm aware of that HTC listened to us in the forums regarding reload times is when the M4A3/75mm and the M4A3 (W) 76mm were released. HTC had the reload times set to exactly the same. Enough of us presented a few "common sense" stuff (cartridge length and weight comparisons, etc) and it may or may not be the cause but HTC increased the reload time for the M4/76mm from 4 seconds to 5.4 seconds the very next patch.
Me thinks the Jadgpanther and Jagdpanzer IV 70 both deserve a wee bit of a DECREASE in reload time simply because of the room to operate (as you and others have already mentioned). The Hetzer has been noted to have an oddball set up and HTC chose to give it the 6 seconds like the Panther and Panzer IV F/2 and H.
We can only hope that HTC looks at a multitude of things before it assigns reload times to its AFV models. When a legit source (actual WWII information, etc) says "6-10 rounds per minute", one could assume the faster shooting crews would be the more veteran crews that had high quality training from high quality instructors. In AH, it appears that HTC has assigned the faster shooting ability to their models in most cases, which is good imo.

On that note, there are videos showing a firing rate of about 2 seconds for the M4 Sherman 75mm. There are men walking around outside and their motion is not sped up so I know the footage is normal time. The M4's have a slightly elevated barrel so they are probably firing HE rounds for indirect fire support. Point it though, as a former tank crewman and combat veteran squaddie of mine has mentioned more than once "there is no limit to how fast you can fire the main gun on a tank". You can fire as fast as you can reload, obviously some tanks have better ergonomics when it comes to ammo storage and reloader position in relation to the breach. Also, the breach action makes a huge difference as well, is the ejection automatic or manual? It all adds up.