No real issue with the 4 rules here.
I've always understood the "all guns are loaded" to mean that one shouldn't treat any firearm as a toy or anything other that a weapon.
If being critical of the 4 safety rules I'd suggest they be expanded. The 4 rules cover 90-95% of all firearms and scenarios. However, to me at least, there are few others that need to be covered.
Damaged or defective weapon. Sig 320/Taurus defects can't be adequately mitigated by perfect, in human, level of consistency in 4 rules. As manufacturers continue to push things in terms of design and also in pace of development, this issue will grow in importance.
Holster/unholster. Always look at holstering process from beginning to end and ensure no objects are in way.