From what I've heard, google intentionally screws with timing, who you will be speaking to, and other factors in order to try to understand how you deal with changes in circumstances.
Source: I work for Google. Our daily schedule is packed with meetings and we try to be as on time as possible, interviews (which are something that everybody should be doing) work exactly the same, we don't try to screw people over with bad timing just to "test" them. Sometimes it happens that people miss interviews and somebody else has to show up, this is unfortunately a problem and it shouldn't happen but sometimes it does (accidents and unforeseen things happen). It's not done on purpose.
> Our daily schedule is packed with meetings and we try to be as on time as possible
If Google's goal were to respect the candidate's time, interviewers wouldn't have daily schedules packed with meetings. The less slack in a system, the worse the failures are. That employees try to be "as on time as possible" is a sign that everybody understands the scheduling is unrealistic.
This isn't unusual, by the way. Most hiring processes don't optimize for candidate experience. Or even for good hiring decisions. Indeed, if you take a POSIWID view of typical hiring processes, the point is to make interviewers feel powerful and selecting for people people willing to put up with inefficiency and suspicious power dynamics.