Why isn't the TF2 Oldschool Pack allowed?

[as the headshot machine]

I love how TF2 looks with the 64 bit look, it makes me feel nostalgic and looks pretty cool, but unfortunately Skial blocks it, I tried inputting it onto mods.skial.com but it said the file oldschool_pack_001.vpk was an illegal file. Anyone know what makes it illegal?

 

[Meowcenary]

Some types of mod files can use textures and other things allowing people to use VAC proof wallhacks

What ever mod you're using uses something that could be exploited in that way. It may not be being used in that way but it still has to be blocked anyway to keep others from using the wallhacks