"Fix position when scrolling" isn't working on autolayout

Hi guys,

i have this special scneario on this file: https://www.figma.com/file/71264jNHXxC8G0PDS632wD/Untitled?node-id=0%3A1&t=YOGB4ToYYvRTlV3S-1

where on Desktop(1280) frame there is this node “Made with anima stamp (white)” that has “Fix position when scrolling”, and we do see it on the Present mode in figma.

however, when i look on the node frame numberOfFixedChildren it doesn’t exist. can you explain how can i get this data from the plugin? i think it is connected to the fact this frame is autoLayout.

attached another frame that is simple frame and there the “Fix position when scrolling” really changes the node frame numberOfFixedChildren.

can you explain me the differences?