Why is there still a gray frame after preloading decals?

Here is my script for preloading a bunch of assets:

local ContentProvider = game:GetService("ContentProvider")

local function LoadAssets(AssetList)
    -- Takes an asset list and preloads it. Will not wait for them to load. 

    for _, AssetId in pairs(AssetList) do
        ContentProvider:Preload("http://www.roblox.com/asset/?id=" .. AssetId)
    end
end

LoadAssets({306913868,306913878,306913893,306913917,306913938,306913960,306913987,306914028,306914059,306914087,306914112,306914130,306914146,306914168,306914182,306914209,306914230,306914249,306914258,306914271,306914283,306914295,306914310,306914322,306914347,306914366,306914384,306914408,306914444,306914463,306914494,306914547,306914573,306914608,306914634,306914662,306914680,306914686,306914769,306914833,306914872,306914910,306914942,306914987,306915041,306915077,306915117,306915197,306915235,306915267,306915279,306915304,306915344,306915365,306915380,306915404,306915420,306915441,306915458,306915471,306915486,306915500})

local function WaitForAssetsToLoad()
    -- Yields until all requested assets are loaded.

    while (ContentProvider.RequestQueueSize > 0) do
        wait()
    end
end

WaitForAssetsToLoad()

Here is what the output is:

https://i.gyazo.com/08e3e14a48ae296e9b7cebec40616ee6.gif

Basically, each decal holds 100 frames, and has a X and Y Size Scale of 10. Then my script changes the X and Y Position Scale accordingly.

You may notice the gray frames when a decal is loading. Preloading helped decrease the decal loading time, but I'm not sure why there is still decal loading time.