Now if in you agree with Porygon that all shots fired by vehicle should hit and damage other vehicles pls explain why.
Imo having Luch do damage to IS-2 with every shot fired would be a very bad change.
Please go back an reread what people have written. No one suggested that all vehicles must have deflection damage. Take the suggestion for what makes sense, not for a super extreme case that has not been fully excluded by someone. Also, please don't state suggestive things about what I have written or intended, if that has not been the case.
As is, deflection damage is generally deleted from CoH2. The all or nothing coin flip has caused lighter units to disappear in the late game since they can barely contribute to the foght anymore. They become pop cost inefficient compared to higher tier units. The existance of heavy armor then forces all factions to have access to high penetration units, otherwise heavies become a game ender. Those high pen units (TDs and ATGs) in turn shit on medium armor, which is why from 2v2 upwards you'll always see a Panther and Comet spam. Due to similar reasons, other units such as the StuG, JP4 and SU76 disappear from the late game: Because they might be unreliable when they need to perform against heavier armor.
Have a look at the current KV2: Its penetration values are actually laughably bad for such an expensive unit. But the deflection damage allows it to at least supplement and support against heavy armor, being a decent threat to medium armor while dominating none of it. Even a OST P4 can bounce a KV2 shell. The chance of the KV2 triple shotting a P4 is about 35%, so it is there, but more often than not you'll need 4 shots, making the KV2 a deterrent, but not dominating any armor.
The option would be to delete deflection damage, which would in turn force higher penetration to a level that mediums are surely or very reliably penetrated. This decreases the value of lighter units and we loop back to what I wrote above