It's not difficult to understand, it's just meaningless. Neither Liverpool or City would have anything to play for by the time they played Chelsea, so I assume you'd factor that in and give Chelsea a greater chance of winning? Will your algorithm take into account Utd's struggles against lesser sides? And what's 'recent form'? 3 games? 10 games? And why would x amount of games count for more than 28 games?.
Chelsea haven't exactly been consistent all season in the first place, no reason to believe they would win those games even if Liverpool / City didn't have anything more than Pride to play for (and they have Leicester and Liverpool away which should also factor into the algorithm which Im sure doesn't come anywhere near ppg either)
On the other hand , Utd have significantly improved since Jan in goals scored (yes even against the lesser teams, and even beat the team that Liverpool got thrashed by recently, god forbid!!) and less conceded - just because Chelsea couldn't or didn't want to strengthen in Jan , doesn't mean any thing should be weighted much more towards the beginning of the season …...even without those additions Pogba would have been fit for the run in and would have also improved Man Utd significantly over the comparable matches from the start of the season, not to mention formation changes which have also helped Utd recently.
Given Utd also had Leicester last match of the season - and their form had dipped (they won one in the last 5) its not inconceivable Utd and Chelsea could have been above them too - 6 point gain in 8 games to make the head to head interesting...….certainly not impossible by any means.
Im sure there are just as many combinations for Europa and relegation places.
Personally I say promote two (or three) from the championship , don't relegate anyone (even if that means every match week one team doesn't play) and relegate 4 or 6 at the end of 2021. I understand the EFL Cup is going soon anyway so scrap it next year (at least for EPL teams) and friendly internationals and you should be able to make up enough additional match days to accommodate.
edit - yeah Utd have been ****, beating Chelsea and Man City three times each this season, Ole has grown into the position with a very mismatched squad accumulated from 4 previous managers, and found some consistency and managed to get over all pretty decent results vs top six sides and also just working out systems with Jan signings admittedly, that work against those that sit back.