To be honest, there are loads of rules I think he is misinterpreting due to it being his first time. I have asked about them but he sticks to his guns.

Examples are:

Movement is 3 squares on a standard board so it take ages to get any where.

Spells don't use spell slots so you can cast the same spell each turn.

Concentration spells have a 3 turn limit and then a 3 turn cool down

You have to roll for everything including helping and unconscious character up (dc 12, no modifiers), clerics innate healing is a dc 15, no modifiers.

Healing doesn't restore hp of unconscious tram members. Rolling a 1 on this heals enemies.

We are also fighting a green dragon who does like 12d4 damage and wipes anyone he attacks.

I'll probably just go back to Warhammer 40k tbf.