Comment by amiga386

Microsoft Solitaire (Klondike) frequently gives you unsolvable hands, especially if you're using Draw-3.

FreeCell "is fundamentally different from most solitaire games in that very few deals are unsolvable" (https://en.wikipedia.org/wiki/FreeCell) i.e. most solitaire games deals are unsolvable.

As you said, Microsoft FreeCell does only deal one unsolvable puzzle as standard (#11982 out of 32000) https://www.solitairelaboratory.com/fcfaq.html