No unfortunately that may not work. Even if you revert all updates, the old launcher now has the ad. It appears they are doing this from their service side somehow. I removed all updates and disabled updates, but it didn't work. Mine required side-loading a launcher.

You have to also revert the play services app and then disable it, in addition to reverting the launcher app.

I've got some other apks disabled as well, but I think these two are the critical ones.

I haven't had the ads pop up again in over 2 weeks.

I'd be curious if it depends on when you purchased the shield. I just tried this on my older shield reverting/disabling worked, but my newer one does not.