If we had 9-bit bytes and 36-bit words, then for the same hardware budget, we'd have 12.5% fewer bytes/words of memory. It seems likely that despite the examples in the article, in most cases we'd very likely not make use of the extra range as 8/32 is enough for most common cases. And so in all those cases where 8/32 is enough, the tradeoff isn't actually an advantage but instead is a disadvantage - 9/36 gives less addressable memory, with the upper bits generally unused.