You can't tell. That's my conclusion too and hence if that image was part of the VAR review then the goal should have stood. If you can't determine whether Aguero is goal-side or not, from that image then that suggests he's level.
A good job it didn't matter in the end but having seen two VAR calls for City in days go against us, and two VAR calls go in favour of Real Madrid, I am thinking that human interpretation is biased. The goal-lone technology, and the hawkeye in tennis are perfect applications of technology to sport, but VAR doesn't seem to be ready. The images and decisions should at the very least be accountable and open afterwards so we can assess whether it works. If they are not making that info available to football fans, then I hope at some level someone is checking that the right decisions were made. I hope City are asking questions too because we can't assume that someone else is.
If I were a journalist I'd be looking at the implementation of VAR and analysing the calls, and seeing which teams benefited and what the success rate was etc. Anecdotally, the most popular club Real Madrid has been the major beneficiary, and the most unpopular club Man City, the biggest loser in recent days which in of itself should set alarm bells ringing.