POWO and World Plants consider Polygonum aviculare var. depressum to be a synonym of Polygonum arenastrum. While I understand that the taxonomy of the P. aviculare complex is still contentious, that one of these two taxa are a synonym of the other is does not appear to be, so only one should exist in the iNaturalist taxonomy.

Consider the community already seems to lean heavily toward P. arenastrum (see discussion in https://www.inaturalist.org/flags/608807), it seems appropriate to lean that way until someone publishes some additional information on the taxonomy of the complex.