At least according to news reports at the time, Stritch was up for the London production.
Maggie Task was actually the first Miss Hannigan. That was at Goodspeed. I don't think Stritch was ever under consideration to be the first Broadway Miss Hannigan. I seem to think that it was Mike Nichols who said, "Dorothy Loudon," and that was it. News reports later said that Stritch was offered the role in the London production. Rumor had it that they couldn't come to an agreement on money.