Ok, so I found out that you CAN summon hisuian forms. So far I managed to summon Growlithe and Zoroark, testing out Ash Greninja (which does exist) and Hisuian Typhlosion
[Hisuan Zorua 1.0.1]
08000000 03075530 00000001 0000023A
[Hisuan Growlithe 1.0.1]
08000000 03075530 00000001 0000003A
[Hisuan Typhlosion 1.0.1]
08000000 03075530 00000001 0000009D
[Ash/Battle Bond Greninja 1.0.1]
08000000 03075530 00000001 00000292
Note: While you can encounter Hisuian Typh, note that you cannot get it in its baby form.
View attachment 338210