Storm is right, foot faults have different treatment, common sense plays a role. First, I can recall a University of Minnesota player winning his match in the NCAA tournament when his opponents was called for a footfault on his second serve on match point. The player said that the woman who made the call wasn't a relative of his and he didn't know why she made such a call. He did NOT say something like, "Oh, well maybe he DID footfault." Players know that you don't call a footfault on match point, (maybe an outrageous one). But allow the point to get played.
To my surprise I learned that baseball umpires do not call a fielder on not having his foot on 2nd base during a double play. It's ok for him to straddle the bag. They feel it's better for the game to be played. I suppose this is analagous to teaching a child about lying. Simple people feel that lying is never right. Adults know that there are exceptions. The same with rules on footfaulting, and really, all rules. Yeah, rules are rules, but rules are made to be broken. The article I read says that replays reveal that there was no footfault. This means that there certainly was no obvious footfault, and that it didn't make any significant difference in the quality of the serve. You'd call a footfault in that situation because you think there might be a footfault? Very poor judgement. How did such a person ever get allowed to officiate such an important match? Tennis needs to have officials with some training and knowledge.