I believe it's like a filter which briefly lets light pass through, twice, although the way they achieve this is weird. In conventional double-slit the 2 splits have different x positions, here they have different t positions.
A rolling shutter doesn't cause changes in frequency of the light itself.
The temporal slit appears to be causing frequency changes in the light beam. These frequency changes then interfere with each other creating a diffraction in the spectral frequency (rather than by physical distance as is with the traditional double slit experiment).
The diagram of page 3 of this helped me understand: https://arxiv.org/ftp/arxiv/papers/2206/2206.04362.pdf.