Just a quick observation.
If you go to table 1, you will see that there is no sample that says 'West' that has G2 haplogroup.
SE has more G2 than NE, but that's secondary. The main difference is West/East.

By the Middle/Late Neolithic, there seems to be a divide between the Atlantic/Northern Plateau, and the Mediterranean/Southern Plateau in regards to Y haplogroups.

By that time there has been the "resurgence in WHG ancestry" compared to the Early Neolithic, that many papers talk about.

One possible explanation is that the EEF had a harder time settling N Iberia, or at least, their rule was more unstable.
So the WHG resurgence could have started there, and even meant the total replacement of G haplogroup there.

While I2 haplogroup could have had a refugia in the Atlantic region. The same region of I2 Megalithic cultures.