There are several posts about vacuum sealing the hops at home, apparently with good success. Are these bags oxygen bags true oxygen barriers, or it that really not necessary?I have to assume that they truly are oxygen barriers. When you seal a bag of hops, the bag is sucked clean of O2 (or at least as much as the sealer can) and the bag itself is hard as a rock. I have had "bad seals" where it looked good at first but I go back into the freezer the next day and the bag is soft now so O2 got in where the seal was. But if the seal is good the bag remains very hard and packed. If O2 were getting in through the bag material I assume the package would be soft in a short time. I hear you though: Many packages are more foil-like O2 barrier material which seems like it would be better but the plastic bag material for the sealers seems good to me.
Ahh, some good old Fick's Law (https://en.wikipedia.org/wiki/Fick%27s_laws_of_diffusion
Anything can be an oxygen barrier, just being a barrier doesn't mean it stops permeability, solubility and diffusivity, only (possibly)slows it.
In this case, food saver bags are made from Polyethylene (and some nylon).
The oxygen permeability of it is: 2325 (cc 25μ/m2/24h)
Mylar on the other hand, permeability is 16 (cc 25μ/m2/24h)
So that means food saver bags are 150 times more permeable than mylar, neither of which however, are impermeable
Once harvested, hops (like all agricultural products) have a declining state, oxygen starts the reactions, and in this starts the degradation of hop polyphenols, and acids. This is why we have a index for hop aging degradation.
Temperature greatly helps( or hurts) this due the slower reaction rates based on (colder)temperature, using some kind of barrier also greatly helps.
Most people at home us vac seal bags due to usability, most commercial hop solutions come in some type of mylar/N2 purged bag due to shelf life, and product quality.
Life is always a trade-off
Use what you got, anything is better than nothing!