I’ve gone the other way when need be. 2.5A Micro USB power supply with a USB C adapter to a Pi 4B. I was able to get a Pi 4B but the Pi 4 power supplies were out of stock. If I had waited for the power supplies to be in stock the Pi 4’s wouldn’t have been. ;)
Even working hard a Pi 4 isn’t going to reach the 3A or 2.5A limit. Not by itself anyway. The 3A limit is there for the power hungry peripherals like motors, servo’s, etc.