I don’t think that’s the case. This is the first time I’ve downloaded a snapshot version of GregTech in years. I also have Firefox set up to clear my cache every time I exit the browser, so there’s that as well.
I also checked the commit hash (574aedd8) from the in-game version string (see the second screenshot in my previous post above) and it matched this commit in the GregTech 6 repository on GitHub:
commit 574aedd8c32f4a1bab775417f94062fc7d35ffd3
Author: Gregorius Techneticies <gregoriustech@gmail.com>
Date: Mon May 3 07:46:27 2021 +0200
This should fix Tooltips crashing without throwing any exceptions
As for the problem of people downloading a cached version of GregTech, you may be able to fix that by using a cache-breaker / cache-buster. The simplest way I can think of to accomplish that is to replace the link to the snapshot .jar on the secret download page with a <script> on the page that writes that same link, but with a query parameter (cb) whose value is the current Unix timestamp:
document.write( `<a href="https://gregtech.mechaenetia.com/com/gregoriust/gregtech/gregtech_1.7.10/SNAPSHOT/gregtech_1.7.10-SNAPSHOT.jar?cb=${Date.now()}">Download</a>` );
Alternatively, there are special headers (like Cache-Control) that can be used tell browsers not to cache a requested resource. You can accomplish that by configuring your webserver to send that header when that specific URL / a URL beneath the snapshot directory is requested. I’m not as well versed with Cache-Control and its related headers however so I doubt I could be of much help there.