Something that is frozen solid isn't going to spoil in anyway in 2 hours. I carefully monitor the feeder after 2 hrs. exact. And since it is currently mice I am feeding that is usually just the right amount of time, but with small rats it might take a little more time. Once the belly is real soft I then immediately start heating with the hair dryer or heat lamp.
I agree with you somewhat for instance I don't think you should leave a f/t feeder in all night like some suggest or do. But I haven't had any problem of refusals using my 2 hrs thaw over the enclosure method. Bacteria doesn't really start in food (that has reached room temp) until after 2 hrs. But these are starting out solid frozen at the beginning of the 2 hrs. True, water is a faster method but for me ours is easier to do. And that 2 hrs of letting the snake sniff it really does help. IMO Using this method with my latest snake I haven't had any refusals or regurgitation's and I have had this particular snake almost a year now.