I play many games flawlessly or with a couple of minor mistakes but very rarely do I play a flawless or near perfect multi-point match. The reason is that some games consist solely of positions and moves that occur so often that they become standard. Such a game will be played perfectly. Most matches take a player into unfamiliar territory and that requires thinking and judgment. Such games generate mistakes.
When checking out someone that you suspect of cheating it's best to look at enough matches that you are feel both convinced and that you could convince others if required to do so.