You don't need e-marking for 3A charging. A non e-marked cable can deliver up to 60W (3A@20V). It must route the CC pin to be able to negotiate a higher voltage (>15W 3A@5V), but this is (spec) required for all USB-C cables.

Edit: I should add that it is possible for a fully complaint combination of devices to not charge at max(sink power, source power), because not all possible combinations of voltage and current may be supported. For example a 60W charger may support 20V@3A, but if the 60W sink only supports 12V charging, it needs 5A and this combination won't support 60W charging. In practice this should be rare though, it would be terrible product design.