I would say that whoever said that didn't know what they were talking about.
Lucas (or any manufacturer) would not risk the liability of selling a product that could potentially damage engines. Even if they have a waiver on the bottle, people would not buy it or use it.
Buy what you can or want but neither of those products is going to hurt your engine.
70 Challenger RT 440-6 EFI, 73 Cuda 416-6 EFI
05 Hemi Durango, 01 Ram 4x4, 14 Ram 2500 4X4, 10 PCP Challenger 6 spd RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR (under const)
9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)