I agree with others 65gr and higher are heavy for cartridge .
I'd first say don't confuse optimal/best with anything lighter won't work . IMR=4064 will shoot 55 , 60 , 62gr bullets just fine it's just a tad to slow to be "optimal" for those lighter bullets .
Second I'd say long extruded powders like IMR-4064 fill the case fast and the heavier the bullet the longer the bullet . This means the deeper in the case the bullet will sit/seat . That can be an issue if you are using a powder that bridges in the case and leaves air pockets of space in the case . This results in not enough room to seat the bullet as deep as need be for ... lets say mag length for an AR .
Example :
This is how deep a 77gr smk needs to be seated in order to feed from an AR mag . If your powder fills the case to the bottom of the neck , it's going to be pretty hard to seat that long bullet in there .
There are ways to get bulky powder to settle and allow for more room in the case to seat the bullet . Powder funnel with 12" drop tube helps and some guys will use a 36" drop tube . You can tap the sides of the case or vibrate the case to force the powder to settle .
My over all point is many powders that are best for heavy bullets for the 223 will likely need compressed loads , All my 77gr 223 are compressed by at least some .