Are there more high nines in pai gow tiles?

Hello. We've been studying the optimal house strategy for the dealer as banker and have gotten confused about the high nine. In some cases (with H4, H8, 9 and H10, for example), the strategy suggests playing 2-9, instead of 4-7. We would have thought that the best low hand would be the right strategy, unless the nine were a high nine. This particular 9 isn't a high nine, but the strategy seems to treat it as such.

The same happens with H7, L7, 9 and H10. We would have thought the best hand would be 6-7, but the strategy indicates 4-9, almost as if this were a high nine as well.

Are there some cases when a non-high nine is treated as a high nine?

The optimal house strategy is based on what the math indicates is the best play, that is, the play which earns the house the most on average. The traditional house way is just that, a traditional way, not necessarily the mathematically best way. It consists of a few simple rules. The optimal house way has so many oddball plays that it's virtually impossible to boil them all down to a few simple rules.