If you are explicitly defining "sound" policy as following the mandate then their intent or reasoning is irrelevant. According to this logic, they failed to reach 2% inflation for most of the last 10 years and therefore the policy was unsound.

As you'd be right to point out, almost nobody defines monetary policy in these terms, but it's your definition. The fed balance sheet is 1/4 the size of the total economy, the over night rate is so low that OMO only works in one direction, it takes more than 1.5 Trillion dollars of reverse repo a night to keep banks in operation, and the Fed is so backed into a corner that they purchased bonds and didn't raise rates (expansionary) in January while inflation was at 7%.

Meanwhile former Fed board members, former treasury secretaries, and basically every macro bank analyst in existence is commenting that the Fed has made it's biggest policy error of all time.

So sure, keep arguing that they are doing "sound policy" whatever that means. Most people aren't going to buy it.