You're not supposed to go that way.

Wat?
That's where you go in the original Half-Life 2?
The fence is even bent so you can crawl trough?
https://i.imgur.com/b4x6Agn.png

You're at the wrong fence mate, look at the images side by side. In the original HL2 pic the fence is bent at the top and at the bottom. On your pic only the top fence is bent, while the lower fence is still upright.

Unless the Gmod half life 2 map differs from the original, you're in the wrong spot.

Either way this isn't my mod's fault, it doesn't change anything about the maps at all.

I loaded up the map with all my addons disabled and that seems to be the case. The fence in gmod isn't bent by the stairs so you can't crawl trough it... strange