sharedStorage.selectURL() now allows queries to be saved and reused on a per-page basis, where the two per-page-load budgets are charged the first time a saved query is run but not for subsequent runs of the saved query during the same page-load. This is accomplished with a savedQuery parameter in the options for selectURL() that will name the query.
Without browser support for saved queries, web developers using sharedStorage.selectURL to make the same query more than once in a page load, and wanted to do so without depleting their site's page load budget for shared storage, would be incentivized to develop their own methods to reuse queries without additional budget charges. These ad hoc methods would involve storing information bits ex filtrated from selectURL via mechanisms such as using an iframe to load the an opaque URN, or sending event-level reports, that are not intended to be permanently available. We don't wish to encourage the active reliance on bit ex filtration methods.
Explainers: https://github.com/WICG/shared-storage/pull/176