Initial Retrieve request response 'minimal'; subsequent responses return expected content

[jennr]

We make a Retrieve request right after a Subscribe request and receive responses like the one below. Afterward, if we Unsubscribe, re-Subscribe and then make a new Retrieve request it outputs as expected. Is there an undocumented wait period suggested for Retrieve calls made after a Subscribe call?

    "status": {
        "entriesCountSinceLastMaintenance": 0,
        "velocity": 0,
        "popularity": 0,
        "lastParse": 1238451905,
        "period": 4,
        "lastMaintenanceAt": 1215824721,
        "feed": "--rss-feed-address--",
        "lastFetch": 1238451905,
        "code": null,
        "title": null,
        "nextFetch": 1519077194,
        "http": ""
    },
    "title": null,
    "updated": "",
    "standardLinks": {},
    "items": []
}