Chromecast with Google TV is now serving full-screen, auto-playing Chicken Tender Wrap ads
(www.androidauthority.com)
I bought the Chromecast with Google TV (older version, not the newer 4k one, which I also own now) when it first cane out.
The home screen hasn't changed since day 1 when I plugged it in.
It always had an ad at the top, and you always have had to purposefully move the cursor onto the ad itself and not touch anything for multiple seconds before it played.
I owned the OG chromecast and chromecast 2 before that, and you are right, that one didn't have ads, but it also didn't have much of anything really.