Probably right about the fabric/plastic boots reducing the types of shoes Sno-Seal will seal.....but here in Texas, we wear western (cowboy) boots and nothing rejuvenates and protects leather better than a beeswax based sealant like Sno-Seal. A wash with saddle soap, then a rubdown with SS (i like the smell too!) brings boots back to new again.
I remember back in the early '70's, an article in The American Rifleman gave instructions on making your own beeswax boot waterproofer that looked and smelled the same as Sno-Seal. Even the ingredients are hard to come by now. Beeswax, neatsfoot oil, a dab of paint thinner as a carrier.
I typically slather on the Sno-Seal and then follow up with a hair dryer and it soaks right in. I know I can mail order the stuff. Just wanted to buy some locally. A can lasts a few years.