And then they see the depth of the impression and work out weight of individual. Not a small person but a man about xxx pounds and based on typical proportions a fairly narrow height range. I seriously doubt law enforcement, at a particular training level, would be fooled that easily. Especially the law enforcement likely to be looking for the unabomber.
Probably the best disguise is being average shoe size and average weight wearing a very common shoe brand. If you're lighter than average a rucksack of weight. If you're heavier lose weight before your bombing campaign. I'm fortunate in that my shoe size is very average. I'm tall but not overly heavy so perhaps a fat shorter man based on my footprints.
I have not given this much thought and I'm not on the run. Just to clarify. Besides for some reason I'm memorable. I often got greeted in the past by ppl I've never met who knew me like a friend. University years well spent?! Anyway I'm possibly not a good build to pass unnoticed if I was a terrorist or bootlegger type. Mind you one of my American ancesters did earn a bit selling illicit alcohol but she was an old lady then and sold to the great and the good so was protected! No fast car or funky shoes needed. I could imagine the car chase. A little old lady, barely able to look over the steering wheel, getting chased by cops in her Sunday best car at a few mph! Eventually stopped, but making a move sale in the process!