It doesn’t make sense for her to say that. According to google Robert is 1.84 meters tall and Sarah is 1.7 meters tall. That’s 1cm over 6 ft for him and just about 5’7" for her. Why would he stand on an applebox? Does he need to tower over her? Also looking back at the episode he appears about 5 inches taller than her in most shots where they’re standing together so he doesn’t appear to be using an applebox. I think she is misremembering.