He's right, though, isn't he? Not sure why you'd say he doesn't get average. "Averages" would require you to consider the probability of penalties being scored - which is high. I think a penalty has an xG of .76 or something. As such, on average, 76% of penalties are scored. This would include some where the striker misses the target. So, on average 2.4 of 10 penalties really should be saved. Now, you could consider that this xG may include (I don't know if it does) stats from shootouts and from poorer quality leagues. As such, you could reasonably assume that the xG should be higher for league games where you only face guys that are designated takers and therefore more likely to score. If so, you're down to what he's said - 1 or 2 per 10.You don’t get averages, huh?
Note: A penalty not being a random event / game of chance does not have a 50% probability of being scored (the simplistic view of "given that there are only 2 possible outcomes, each has a 50% probability"). The nature of the event is such that one outcome is far likelier than the other. As such, the average here will be weighted towards the outcome that is more likely. Hence, the average is not 50%, but very skewed.