Recently I changed my control scheme for Destiny 2 (PS4 Edition), to where my melee input is R3 (or down on right stick), my melee ability to R1. Sword light attack is still bound to R1 and it functions fine.
Glaives however do not light attack on R1 the melee/glaive icon flashes red, and instead does it on R3, unless I begin a chain; then it continues the chain on R1 inputs.
The Glaive melee is very similar to a normal melee, so it's normal for the Glaive melee to be used in your R3 example
(if I understood it correctly. Your uncharged melee is on R3 and your charged melee is on R1, right?)