When I get a new message, the first thing I'm going to click when I open the app is the top message - except there's a delay of about a second before the ad appears, which means just as I go to click on the new text, I end up clicking on the advert.
I don't mind having adverts, but this feels mean-spirited and will only push me to another app or an ad blocker, rather than make me donate to get rid of the ads.
(Also seems like it may go against Google admob behavioural policies).