I think it's just that in her Clark relationship she's always kind of playing the same scene. And also, interestingly, she was kind of right in the way Clark's personality worked--which works really well for what Philip is trying to do here. Clark's always on guard controlling the information and it rules his whole personality--because Clark is supposed to be this very officious pencil pusher who has nonetheless broken a big rule. Like in a way Clark is like a regular person being a spy like Philip, but he's not good at it so he's stiff and careful about everything. And there's a formality that also seems to go alone with Clark trying really hard to be the best government hall monitor he can be.

Where as in this scene Elizabeth presented Jennifer as being the normal member of the family who doesn't have those constraints because she's just a girl visiting her sister in law, so Martha could speak from a different pov.