When using an element as a pattern source, the pattern currently doesn’t respond to variables applied to that source - for example, if the source element uses color variables that switch between light and dark mode, the pattern doesn’t update when the consuming frame changes modes. It seems the pattern references only the visible state of the source rather than the variable-driven values.
It would be great if patterns could follow the variables applied to their source, so that they update correctly with light and dark modes.