MagSafe official accessories have to have an NFC chip that Apple certifies so iPhone recognizes the accessory and will use it at high speed with MagSafe - it’s shown and described in the keynote and the iPhone web page. If the iPhone doesn’t recognize the MagSafe charger capable of up to 15W, it will only draw power as Qi instead at maximum 7.5W for safety reasons (15W wireless charging was basically unheard of until recently because high wireless wattage emits lots of heat, so the efficient alignment is a must to concentrate the power transfer). The NFC chip is what makes iPhone go from sticking to any old magnet and Qi charger made by any company, to instead showing the animated MagSafe charging screen and pulling 15W. Same NFC chip is in the cases too - it’s how iPhone knows it has a brown case attaching and can show the matching color when you put it on the phone.
iPhone will not pull high wattage from just “MagSafe compatible” wireless chargers with magnets - it must recognize the MagSafe chip. iPhone will only pull its maximum Qi power draw of 7.5W if it is just sticking to a charger without true MagSafe.
So yes, these unofficial chargers that are just Qi with a magnet will be slower than using actual MagSafe if that interests you.
Also not that Qi 7.5W does not actually charge at 50% faster than a 5W charger. Wireless charging is inefficient and gets worse with a case on. MagSafe has this issue too, but far less so at double the peak transfer. It may matter to anyone who is obviously here looking for MagSafe stuff.
View attachment 1667040