Pre-lubed Hydraulic Lifters

I don`t understand why you would bend a pushrod if prefilled.
Solid lifters bend pushrods? what's the difference?
On hyd. maybe if using aftermarket adjustable. I`d imagine most will tell you to measure for correct length.
Most recent set I installed, the manufacture recommends not filling lifters. I tend to just follow instructions if provided.
I wonder what changed from back in the day to modern lifters, that require not prefill?