I love the APLT and wouldn't want it changed, but essentially you're benchmarking against last season's teams. An away win against against last season's bottom half team is a par 3 that you really must win, yet this season one of those teams (Leicester) has really raised their game and are second in the league. It's a really tough match.
Likewise a top team has turned to sh*t and a visit to their stadium is a bit of a holiday. No guessing which.
(**Cough** Chelsea).
Some of it evens out, and the table is an excellent guide to early season form.
It's not bottom half teams, it's the three promoted sides and the lowest four surviving teams in the league last season. Leicester finished 14th last season, if they'd been 13th they would be a par 1. The others are Newcastle (currently 19th) Sunderland (currently 17th) and Villa (currently 20th)
As you say, Chelsea are 14th at the moment, which would make them a Par 3 visit, but they won't be there at the end of the season.
Newly promoted sides are always Par 3. They rarely finish in the top 13 at first attempt, either.
The previous year saw Newcastle in 10th and West Brom 17th, otherwise the Par 1 sides were the same.
You very rarely see more than a couple of sides change places in or out of Par 3 status.
14/15: Leicester, Newcastle, Sunderland, Villa
13/14: Sunderland, Villa, Hull*,
West Brom12/13:
Southampton, Villa,
Newcastle, Sunderland
11/12:
Stoke, Wigan*, Villa, QPR*
10/11: Bolton*, Blackburn*, Wigan, Wolves*
Teams in bold finished 13th or above the following season. (4 out of 16)
Teams marked with * were relegated the following season. (6 out of 16)
So it's actually more likely that Par 3 sides will get worse than that they will get better.
It isn't perfect, but the model is actually very robust when measured against reality, all it means is that typically one, or at worst two, of the Par 3 games should be Par 1s, but there is always a corresponding Par 3 game which "should" be Par 1, so it balances out.
Of the 3 APLT teams to visit Leicester so far, Spurs and Man Utd have drawn and Arsenal have won. It's a tough Par 3, no question, but I'd still expect a side with realistic title aspirations to go there looking for a win.