A technical grade is something that is used for laboratory consumption. It's concentration may vary depending on the need of a certain laboratory for research. For example, the reagent sulfuric acid as a technical grade can have different concentration for different uses. It can be 18 molars which is the most concentrated one or it can also be in lower concentration depending on its use.
However when we talk about commercial grade chemicals, these refer to the substances that we use for daily consumption. The commercial grade hydrochloric acid (muriatic acid) cannot be in its highest concentration unlike in technical grades one. It occurs in 29-30% maximum content in a given solution.
In summary we could say that technical grades are for laboratory and research consumption; thus may have a variety of concentration to choose from. While a commercial grade is for daily consumption; thus lower concentration is used because it is already in a solution form.