What system is this expert using?
Stewart's recommendation is reasonable in any standard system, whether 1NT is forcing or not.

Unless your partner's hand was very unusually distributed, it sounds like your partner was at fault for reversing with only 13 points.

Reversing means bidding at a new level (here 2 spades over 1 NT) in a higher ranking suit (spades ranks higher than hearts) than your opening bid. In essentially any natural system this promises 16+ points.



Why is even a forcing 1NT not an issue?

The hand shown has a 7 card club suit and two singletons. Whether 1NT is forcing or not, this hand expects to play best in clubs. Two clubs directly shows too much strength. Bidding 1NT followed by Clubs (presumably 3 Clubs) typically shows this type of hand.

There is a decision whether to ignore the 4 card spade suit or not. Once the hand is this distributional it can make sense. You'll have a hard time getting to clubs after you bid 1 Spade because a second suit by responder usually shows extra strength (and is often artificial).

Notice that if you had had the same hand but with 3 spades and 2 diamonds, there would be no question that 1NT is the bid.