You should look again, perhaps at better images, and/or on a better computer/monitor. Your concern is unfounded, as every Surly "touring" fork with a mid-leg mount has the type which passes all the way through the fork leg. Here are eight examples, and you should be able to see the boss protruding slightly on the inside of the fork leg in each listed model of fork, which naturally includes LHT and Disc Trucker:

https://surlybikes.com/parts/forks#touring_forks