The iphone12 can't be charged with 40w fast.
iPhone's fast charge agreement is PD agreement, and 40W charging plug is not compatible with PD agreement, can not give 40W battery charging rate, usually only supply 10W battery charging output power, so iphone12 can not use 40w fast charging.
Apple does not support 40w fast charge.
In general, between different brands, the fast charge agreement is not the same, so Apple can not use a 40-watt charger. Moreover, the other is the typec interface, and Apple is other excuses, not suitable.