Luck can change throughout a season. Max had horrendous luck earlier in the season, but recently had good luck with the rain in Sochi. The poster was simply saying that currently it's favouring Max, and for the title race to be anything other than a formality from here, it would require Max to switch back to getting bad luck.
The luck Hamilton vs Verstappen - breakdown:
Italy - Hamilton runs into a wall and was set to come out dead last, also needing repairs and would not have any points - BEFORE Bottas instantly saved him by crashing with Russell causing a red flag, free repairs and no more positions lost for Lewis.
Points gained by Hamilton in the championship: +19 (VER 25, HAM 19)
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Baku - Verstappen looking to win the race and take 25 points vs Hamiltons 15 before his tire blow out.
Points gained by Hamilton in the championship: +10 (VER 0, HAM 0)
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Silverstone - Max leading the race setting to bag 25 vs 18 point to Lewis, before Lewis is causing a collision and is deemed guilty.
Points gained by Hamilton in the championship: +32 (VER 25, HAM 18 - became HAM 25, VER 0)
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Hungary - Hamilton looking set to win and take 25 vs 18 Vs Verstappen before Bottas takes out both Red Bulls.
Points gained by Hamilton in the championship: +18
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Monza - Hamilton set to score more points than Max before the collision. HAM 12 - VER 10)
Points gained by Verstappen in the championship: +2
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Russia - Verstappen set to finish 7th and Hamilton 2nd before the rain comes in, HAM 18, VER 6 becames HAM 25, VER 18.
Points gained by Verstappen in the championship: +3
Total summary of points gained by sheer luck: Points gained by Lews
79 Vs Points gained for Verstappen
5.
Note, you could even note any points gained by Verstappen in Russia should not count because the engine change was a direct result of a Hamilton punished error, meaning Hamilton was responsible and lucky Max had to take an engine penalty.
If luck was not a thing the current championship standings would be:
Verstappen: 346.5
Hamilton: 262.5
Which leads us to
The Hiltons next point:
The only reason the championship is even close is due to the DNFs for Max, otherwise he'd have it sewn up by now - the Red Bull has been a much faster car this year, with a couple of exceptions in recent races.
You are absoulely right Max would have already clinched the WDC-title if not for all the bad luck explained above, but you are wrong about the reasons.
The reason Max would have won is that Lewis has made so many errors that without incredible luck would have given Max an aprox 70 point swing in the championship.
Mercedes has had the better race pace except for Baku and Monaco, Bahrain and Red Bull Ring x2. At Zandenvort Red Bull won on strategy, the Mercs were insanely quick.
Conclusion, the reason Verstappen should have clinched the title already is not because Red Bulls car has been better than Mercedes on the whole, its because Lewis has made endless of errors that he was incredible lucky not to pay for. Verstappen has been pretty much error free and outpeformed Lewis in every capacity, sadly that might not be enough to win the title because of Mercs unreal engine advantage.