Index combo options always routed to PSE for IBKR

Does anyone know why? It seems smart routing has no effect on option combos

 

What indexes trade on PSE, which I assume is ARCA? Do you mean Options on ETFs?

 

NYSE ARCA did the most volume Friday on Equity/ETF option volume.

 

SPY QQQ IWM

 

I assume if all your orders are going to that one exchange, either their system expects more fills or the DMM they use has the lowest cost of execution at NYSE ARCA.