Yeah, I guess he used the same algorithm for all GPUs but the most profitable algorithm varies from GPU to GPU (Model/Manufacturer).
Also to mention is that you can easily re-sell your GPUs without a very large loss of value if it's still in good condition while ASICs will lose much more value depending on the difficulty and the possibility of forks to ASIC-proof algorithms. In the last case you may end up with a useless piece of electronic scrap.