MORE VALVE TRAIN QUESTIONS................

Direct Connection (I'm aged), had sold a pushrod kit that had the cups separate, allowing you to trim the tubes to size then drill for a light interference fit of the cup stem. I have taken them apart before, trimmed to size and reinserted the cups with a drop of blue Loctite. The cup stem still required a light press to slide in but I used Loctite for insurance. The picture you provided looked like the adjuster's 5/16" ball was sunk into the rod cup and is why I questioned it for verification. The difference in radius between .3125" and .375" is small but could be enough to ruin your day.
I hear you. In order to get my new comp cams apart, I suspect the I would have to lightly heat the cup end of the pushrod to overcome the "press fit". By applying heat, I would then question the integrity of the pushrod metallurgy. The damn problem is, if it fails........Big bucks! LOL