It's not a complaint unless he's complaining. Stating a reason why you prefer one over the other is an explanation, not a complaint. If I say, I prefer rolling because it's more realistic and that point buy/arrays are very unrealistic, which I hate, there's no complaint there. There's nothing about the situation which is unsatisfactory or unacceptable, as I can use rolling which IS satisfactory and acceptable. Now, if rolling wasn't an option and he came here saying that he hates point buy, THEN it would be a complaint.
com·plaint
kəmˈplānt/Submit
noun
1.
a statement that a situation is unsatisfactory or unacceptable.