I believe its because of TEF results which came out on 21st Sep as its not frequent like ielts so probably lots of applicants upgraded their score worldwide ...Actually the increase was a bit steep.
You need to consider 2 things.
1. There was no 3 weeks gap between normal draws
2. There was no significant decrease there (yes 2 weeks before it was 3500, but this week it was 3900, which makes it an average 3700 for each draw)
Now compare the behaviour during this summer where the amount of ITA were more or less the same but you did not see such movement upwards).
So yes something must have change in the system that helped lot of people to get 445+ And that would be IELTS on computer (as there is no other significant change we know about).
Secondly, when you look the total size of EE pool and compare it before 2 draws happens (this week normal draw and FST draw). it did jump more than normal.
So that would again point to a change in the system.
So if rounds of English test just became more available to anybody who had the money for it (and that was in some cases the only reason why people could not get better score - monthes of waiting to get a date for IELTS exam), this will push competition up.
Of course once you see the bigger jump up within first 3 months of new testing availability in place, EE will find new stability point.
Computer based ielts must be contributing although at least in India its still limited to few cities which started a month back ...