I think this prediction is limited to their next match, not to who will win the Premier League. That being said, it is still unclear how Google calculates the winning probability for each match. There is a suggestion that they use historical stats, others predict they use aggregated betting odds from various gambling websites, and so on. I even suspect they use Opta's LWP model to some extent. So yeah, it is still an unreliable metric and you should not use that as a basis to make any serious prediction at all imo.
Survey or things like these are completely unusual because every soccer fan understand how things are going right now who is going to have better chance of winning right now having 83% for the Arsenal after 26 rounds with third spot is surely just laughable with right now we are having all options are wide open and Manchester city is surely having tag of hot favourite and Liverpool is also doing good job with leading the league table.
10th March Liverpool going to host Manchester City and then 31st March Manchester City going to host Arsenal will be give better view about the title race who is going to win this season even still things are tight, and all top teams are having fair chance for staying at the top and winning title in this season with their quality and performance.