According to another forum, this is the origin of most Fantom sounds:
-Bank B contains the first 459 patches from the AX-Edge Keytar
-Bank C is the 128 patches from the Integra-7 Synth Legends expansion.
-Bank D contains the 1109 SuperNatural Synth Tones from the Integra-7 / FA synths
-Bank E contains the 896 patches from in the XV-5080.

I can confirm that the tone names in Bank E indeed match the XV-5080 sound list.

The AX Edge Keytar was introduced in 2018; obviously it has quite a number of newly sampled acoustic sounds such as trumpet, trombone and saxophones, also some strings.
(Note that "supernatural Synth" does not involve the SuperNatural Acoustic sounds - those are definitely not part of the Fantom.)