Is this from personal experience ?
Yes, also personal experience. And for this big difference you do not need any densitometer so see the difference. It is huge. Good point you refer to the Maco website where it is clearly shown that the Pan 25 (v2) film is 1:1 Efke 25 identical.

A few years ago Efke changed the layer for 35mm and 120 roll film to Clear Polyester so these type of films you have to take care of the "light piping " effect. The same for the Agfa Gevaert , Rollei emulsions: CN200 (C41), Redbird (C41, reverse CN200 emulsion), CR200 (E6, older RSXII 200 Agfa type emulsion), Retro 80S, Super pan 200 (identical to Retro 400S), Retro 400S and IR-400(S). All on Clear polyester layer. (S) = Synthetic.