That sentence is not correct.
I revised that bullet point (in #15) as follows:
– The kammaja kāya has all the kammic potentialities (kamma seeds) acquired up to any given time; see “Saṅkhāra, Kamma, Kamma Bīja, Kamma Vipaka,” and “Saṃsāric Habits and Āsavas.” But one of those seeds (which embeds matching gati) becomes operative for the “new bhava” and becomes the “bhavaṅga” for that life. The remaining kamma seeds will retain their gati; each kamma seed embeds the gati at the moment of its creation. One of those will rise to the next bhava or existence; that would be the one best matching the mindset at that paṭisandhi moment. Thus, different “gati” are in different kamma seeds. That is why an Arahant’s mind would not grasp any kamma seed with any gati.
Thanks for pointing that out, Jorg!