FL400 to FL320 in around 2 minutes is approximately 4000 fpm, which is sporty but not particularly alarming, though in daylight 10° or so of nose-down pitch looks steeper than it actually is.
If it had been a decompression at that altitude, I'd have expected a rather more expeditious descent than that (it would have taken over 7 minutes to get down to FL100).
But it clearly wasn't a decompression, given that he levelled off at FL280 for a further 20 minutes.