Yup it is as you have guessed, using the same combination on tarmac will destroy the tarmac, I know because I’ve done it years ago.
You can do it using an alkaline detergent cold water and low pressure, agitating with a deck scrubber but need to flush all the detergent away as it will whiten the area and dry the surface badly if you don’t, although you will always run the risk of some discolouration.
Providing the integrity is still there you can also contract a tarmac company to re spray the surface to re colour the entire area.
Technically already destroyed, insurers will normally go for a test patch and small fee if you want to go for it. However unless its really bad the client will often just keep the money and put up with it.
There may be other ways which I am not aware of, but hope this helps.