It’s also unclear if Kingston was fully aware of the rumors saying Whittaker may exit after Season 13, which would obviously shorten the time window in which these characters can meet.
Season 13 of Doctor Who has been in production for a while, and was slated to run for 10 months when it first kicked off in late 2020.
If Alex Kingston has taken part in discussions about appearing on set for filming River Song’s return, she didn’t indicate as much in her interview, and the implication seemed to be that she hadn’t.