Just because you got LUCKY with plastic and newspaper doesn't mean they are archival materials. The old "it worked for me" defense is not a valid argument.
"Lucky" would probably apply if I had just a few items that were stored that way. That isn't the case. If toy trains were as delicate as you claim, I think they would be ruined by the acids and oils left on them from being handled. I have a friend who only handled his camera collection with while cotton gloves. I guess some train collectors do the same. They are probably in a small minority.
Do you have any photos of items damaged by using food grade plastic bags?
And I missed the part where you explained how trains should be stored. IMHO, telling people they are storing their trains the wrong way, but not telling them how to properly store them is not very helpful.
By the way, don't close the bags. In fact, I often punch holes in them to let them breathe.