People do get it, but having restrictions and a different legal name makes it not the same, these things are known to everyone and creates segmentation, even if by a little. Equalizing name and rights officializes acceptance and nullifies legal differences, this helps further normalization making the homophobic reactions more fringe given they are against something that's official, normal, established.

It's not like people think gay couples were actively shunned and this will magically change things overnight, but as it had happened everywhere else where marriages rights get normalized, it also helps normalizing acceptance even further.