A few issues with that.
#1. There is not even a NET for the first 5 or 6 games. So how would you measure those games -- would you say those are based on year end, but then game 7 is based on "as of played"
#2. You can't use AP Poll as an alternative, because that only ranks 25 or 30 teams each week.
#3. Be it NET, KP, or AP Polls they are not very robust in November and December. They have some value as measures, but they are much more accurate at year end. Therefore it makes more sense to use year end ranking.
#4. Part of the problem is that there is a lot of meaningless games that teams played in their first 15 games... it makes the "as of now" data, even into mid-January, a bit flimsy and not robust.