Yes those "none" covers work like a charm in good to fair weather.
Toss in a decent snow or rain and that's when the "none" brand cease to work as planned.
Ever hear of Rain Guard?
I found that the best way to keep condensation, fog etc. off scope is NOT TO COVER(SEAL) GLASS PERIOD!! I carry a small piece of COTTON CLOTH(like a cut piece from a T shirt) in my pocket to wipe any snow, water that collects on glass. I tried Butler Creek caps, rubber bikini style and whut have ya. I came to the conclusion many moons ago...nothing works best!! For NON-RainGuarded scopes...i use Scope Dope which is a lense paste that is friendly to coated optics. Its now available in a spray. Many professional guides swear by Scope Dope.
I also found that the Butler Creeks extension over frt/rear objective also tends to reduce light transmission which is especially noticed in low lite conditions.
Only reason I ever cover glass if gun is exposed to extreme dust/dirt/grime conditions where i wanna protect glass...which is very rare.