ezo
Hero
Exactly.Yeah, I get the feeling people are really talking past one another and assuming a level of antagonism that may not be warranted. Rules are knowing that different types of armor will have different armor classes. Knowing the dwarves have a different type of armor in this one location, and learn what it does, your characters have to go to that location and talk to someone selling that armor is something to be discovered the course of the game.
Perhaps the PCs have heard rumors of this special armor these dwarves make. Perhaps it is stronger, lighter, doesn't rust, who knows--it depends on what they discover.
Once they go there to see the armor, meet someone who has it, or whatever to GET the armor themselves and equip it, then the DM can tell them precisely (not generally) how the armor is different and impacts the game rules mechanically.
Until then, information is vague:
1. "the armor is stronger and can withstand nearly any blow"
2. "the metal is thinner and lighter, allowing for the same protection as heavier armors but with less weight or impact on mobility"
3. "the armor never corrodes or rusts, and is especially resistant to acids, fire, and cold"
From the information, the players might guess what some of the benefits/changes are, but that's the best they can do until they get the armor.
Once they have the armor, equip it, they can learn the homebrew for it and how it affects game rules:
1. AC is +1 and the armor has twice the hit points as an object
2. the AC is normal, but the weight is half and the armor is usuable by characters proficient in the next lighter armor type, it has no Strength requirement, and does not impose disadvantage on Dexterity (Stealth) checks.
3. the armor is impervious to corrosive attacks, like from a Rust Monster, and provides the wearer with advantage on saving throws against acid, fire, and cold
Notice, the homebrew has impact on the rules, but the rules themselves remain unchanged.
With spells, a homebrew spell has its own statistics, but doesn't change how spells are cast or how concentration works, etc., which would be houserules.