Why the need to protect them from water?

Usually the method of carry takes care of any water concerns, zip lock, match safe, pill fob ... duck tape, aluminum foil
Some methods of carry like zip locks or aluminum foil won't protect tinder if you get fully immersed in water, not just rained on.
Are you sure about that? How do you know zip locks and aluminum foil will leak when fully immersed in water?
The video I linked has the guy fully immersing a bare vaselined cottonball into a bowl of water ... it burns right after
I've personally dunked my ziplock in a bucket of water and it didn't leak ... there is more on ziplocks below
I'm thinking of boaters and aviators, and the kits that would be on their person. See
this video at 3:40That is good thinking

In that video that guy uses cellophane to start a fire, thats practically waxpaper

Doug Ritter often includes zip-locks into
his personal kits Spark-Lite "Fire Tab" Tinders in zip-lock pouch
Doug Ritter
amk psp faq How Waterproof is the POCKET SURVIVAL PAK™ and POCKET SURVIVAL PAK™ PLUS and their Contents?
tested waterproof to 6 ft (1.8 M) fully packed and sealed.
The POCKET SURVIVAL PAK™ PLUS has been tested waterproof to 9.8 ft. (3 M) fully packed and sealed.
Doug Ritter also uses match safes and also vacuum packs backups

See also
Waterproof PSK where falcon5000 goes 8 feet deep with original PSP
Doug also includes a plastic boxed Spark Lite
Aviation ... although the manufacturer doesn't list a waterproofness/submersion rating
Phaedrus, you may have posted it before but what bags & sealing equipment are you using? The setups you've described sound great, although their performance may be improved even more if you add a bunch of smilies...
lol