Sportsbook: Why can’t I ‘dutch’ different selections in the same market with Multiples?

‘Dutching’ involves picking more than one possible outcome in a single race and having the accumulative odds reduced to reflect your increased chance of picking a winner.

On the Sportsbook Multiples product, each selection forms a different line from a different market. Therefore only one selection is allowed from each market and ‘dutching’ becomes redundant.