I only take HCl if the meal had some protein

I personally only take HCl if the meal had some protein in it. If the meal was mixed with some protein and some starch, I sometimes take HCL but maybe a bit less, and if the meal was no protein at all, just starch/veg/non-protein, then I don't take any HCL.

I haven't read specific advice on this, but like you I too am concerned because starches digest best in an alkaline stomach, not an acidic one (proven scientific fact), so therefore it would seem logical to only take HCL when one is eating protein (protein needs an acidic stomach to digest).

None of the silly labels on the bottles of HCL say this, but manufacturers are not known for their label accuracy to begin with.