You can't request 3A via resistors and you don't need to. You can advertise being able to source 3A via resistors. The sink does not advertise how much power it draws (unless it speaks PD), sink's responsibility is to check for what the source advertises (either via resistors or PD) before attempting to draw more power than USB default if you want to be compliant, which boils down to a simple comparator/ADC reading.

Simple sinks just use two 5.1k resistors for pull-downs, no matter how much power they want to draw - and they always need these resistors (two for receptacles, one for plugs), otherwise they won't work with USB-C sources at all.