I have heard a couple of managers mention xG including Allardyce and Tuchel. I am guessing they go into much greater depth though...
Has it occurred to you that some people may be being paid to promote these gimmicks?
Most of the Companies who provide this kind of data are either owned by the Bookmakers or provide services to Bookmakers; for example Opta are now owned by Skybet and Infogol is owned by Timeform which in turn is owned by Betfair/Paddy Power.
Earlier this year I received an unsolicited email from a Scandinavian Company who offered the latest cutting edge data; the Company boasted of the relationships they had with a number of top Clubs throughout the world.
The price of this all singing all dancing data, £400 per month or £1000 per 3 months.
As a teaser I was offered a months supply of their up to the minute, active XG data and the associated selections on the over and under markets; this came with a complete run down on how the data had been manipulated for each game and the rationale behind each selection.
Things went so well during the months trial that after three weeks it was extended for another month; thankfully I had the sense to not risk any money on any of the selections.
Had I bet the selections provided, using a recommended opening Bank of 10k and setting stakes as per the Kelly criteria, which is a formula that calculates how much of your bank to bet on each selection (if you win the amount increases and decreases if you lose) I would have lost over half of my starting bank.
Thankfully the Company stopped mailing me shortly after the trial, but no doubt they are still doing good business; and do not forget that there is a huge demand out there.
The number of people playing the game has been on the decline for years yet the numbers watching the game is on the increase; a lot of people who passed up the chance of playing when they could now think they can compensate by crunching the numbers.
The problem with that approach is one of context.
I work in automotive which is wall to wall lean six sigma, which is a data driven approach to limit errors caused by variation.
The very first thing that is drilled into you is the mantra that data without context is meaningless; not only is it the first lesson you get but it is the most important one.