Why are hydraulic roller lifters, different on different sides in the engines?

I wouldn't think it would matter if the lifter got heavy or light springs, as long as the parts matched that particular lifter body. When the engine is running, the pushrod sits on a head of pressurized oil while the springs are null. The springs just keep a little preload on the pushrod, likely so when you have a cold startup they all don't clatter til you get oil pressure to the upper end and bash the cam lobes. I've seen a couple different roller lifters, but never a different type of lifter in the same engine. If they were all oem lifters in an untouched block, it would mean it was more of a supply issue, where one manufacturer took over the contract and made a slightly different lifter. You received an engine with both types of lifters during the transition. Kinda like my 91' 360, I have a roller cam, but LA style heads. Of course, this was a scheduled thing by mopar. They built the hydraulic cammed small blocks for decades, I'm sure they used lots of different manufacturers. You found a gem or someone else's goofy maintenance.