I have planned Shalane's final couple marathons to optimize her appearance fees, marketing opportunities and potential to finish on the podium.
No spring marathon
NYC '19 (I would expect top Americans to skip fall, especially NYC)
Boston '20 (top Americans running Trials, as well as perhaps other top countries using London for selection)
NYC '20 (few top runners doubling back after Olympics)
Shalane has never avoided competition, so that isn't the rationale. Simply put, she has much less to gain from running the trials. She might not make the team. Or even if she makes it, the reward is running in super hot Tokyo. She can pick her races and be the marquee American and still have a chance to be in the top 5 at NYC '19/20 and Boston '20.