It is not likely that running fan only for 30 seconds a difference. You aren't drying much in 30 seconds and odds are your coils are even still cold from the AC running 30 seconds ago.
Are you preconditioning your car or do you have cabin overheat protection turned on? The smell typically goes away after the first few mins of the AC running so if you precondition you don't smell it. If you have cabin overheat on you don't smell it either when it's hot enough to turn on.
No offense intended, but your assumptions are probably incorrect. I'll explain why drying/warming up the coils worked when all the other things everyone else suggested didn't. And I tried every suggestion multiple times over the last 18 months.
I purposely did not use preconditioning to see if the smell is different. Before doing the ac off ritual it always smelled terrible right after getting back into the car, after the ritual, zero smells. I also don't use overheat protection, fan only mode for that. I park in a climate controlled garage all the time anyway.
My car smelled great for the first year, in the second year of ownership I started using recirculate mode manually once in a while and that's when the smells started.
Here's all the things I tried individually to narrow down the source of the smell or to eliminate it over the last 18 months:
New filters: didn't work, filters didn't smell bad nor were they dirty/moldy, making the old filters wet doesn't make them smell bad either. Myth that the filters get wet inside the car creating the smell is busted.
Anti fungal sprays: tried blasting the spray in from the outside air intake with and without air filters installed. Has limited success, only got rid of the smell for a few days at most.
AC foam cleaner: tried 4 different kinds, they all work for weeks or even months at a time but the smell will come back 100%. The size of the can matters, but >10oz worked best.
Not using manual recirculate mode anymore: once the ac smells, this doesn't eliminate the smell.
Using recirculate mode all the time: this just makes the car smell stale and the terrible rotting smell comes back the quickest this way even after foam cleaning.
Use preconditioning: that gets rid of the first minute of terrible smells, but if I ever forgot to turn it on, holy crap it's terrible! Also the cabin still smells a bit funky anyway with this method.
Don't use over heat protection: mine is only in fan mode, didn't help.
After 18 months of trying all kinds of combinations of cleaners and fan modes, the AC off ritual worked! Just before getting out of the car: Turn off AC, turn off recirculate, fan to speed 10, it won't take long for the air blowing out to warm to ambient (so yes, the coils do warm up quickly, 30s is probably the bare minimum time required). Next time i get into the car, no more smells. I tried this about 10 times, confirmed it worked before posting here.
The car is supposed to do this on its own, but very obviously it didn't work for my car to prevent the smell! And if it did there wouldn't be so many people posting on that's like these.