Yes, the sidewall is thinner. Also does not have the reinforcing that the tread part has. Sidewalls are designed to flex under load and during cornering. The distortion could cause any patch/plug to come loose. I have seen a tubeless tyre with sidewall damage where the owner decided to install a tube and the hole split under pressure and the tube ballooned out through the tear. Ever watch a drag race car's rear tyre in a hard start. A road tyre distorts but not nearly as much.