I have watched with interest some of the many pistol torture tests one can view on youtube. There are some, IMO, valid test points but most seem just unrealistic in real world use. Water tests are valid, we live in a mostly water filled world. Dust, yes, leave anything around long enough and atmospheric dust will coat it. Out in the field water and dust would be an issue.
But it seems to me that covering it in mud or sand isn't something that a pistol would normally have to face in field use. A soldier or police officer may encounter deep mud but will avoid it if possible and probably do their level best not to allow their weapon to be separated from them covered in mud, it would probably be lost.
Would not a more realistic test be something like:
The 2000 round test as outlined in PF.
Hard use jostling, bumps, blows and dropping.
Carried in blowing, dusty environment.
Subject to moisture and loss of lube.
Overall neglect over a set period of time.
Run hard over a short period of time, heat build up, lube burned off then put back in a holster to face further neglect.
Just my opinion.