It actually suffers as a tool by adding xG up. Would you rather 10x 0.10 xG attempts or 1x 1.0 xG? Both add up to 1xG but one is clearly more likely to result in a goal.
It depends on wether you have good finishers in your team or not.
A 1,0xG chance means 1 goal, and exactly that.
10 x 0,1xG chances could be anywhere between 0-10 goals and the better finishers you have the more likely it means more than one goal.
It's a very good tool to measure your chance creation, your players finishing abilities (or hot/cold streaks), your defensive qualities when it comes to conceding chances and your goalkeeper's ability to keep them out of the net. It's by far the best tool we have to give indication regarding this. It is of course not absolute or 100% accurate in the short or long run, but it gets better and more precise the bigger the sample size gets.
This season we've been missing more chances than we should have, with our two main guys up front, Rashford and Hojlund being the main source for that with 1 goal scored from 7,32xG total between the two. This is unsustainably bad (no one is this bad at finishing in the long run). None of them are especially good finishers, but their numbers from earlier season suggest they are around or just below average, which suggest that this goal drought will not last forever for any of them. Having good finishers in good positions is really important though. Right now our two main guys is not. For comparison has notoriously good finishers like Son scored 8 goals from 4,91xG so far this season and Kane scored 14 non penalty goals from 8,95npxG.
The rest of the our team has been slightly overperforming their combined xG with 12 goals from 11,15xG.
I hope Marcus and Rasmus are putting in some extra hours on the training ground finishing, because they need it.
We can also read from the numbers that Onana has gained some shotstopping form the last 7 games where we have won at least 4 flukey one goal wins in bad performances (Not counting the Luton game as that was very one sided): We have conceded 6 goals from 10,73xGA (Expected goals against) in the last 7 in the PL compared to 10 goals from 9,04xGA in the first 5 games.