The FBI has announced that the UC Merced stabber, Faisal Mohammed, was inspired by ISIS, but that there is no indication he was actually a part of any wider terror organization.
If a lone wolf terrorist is inspired by ISIS or any other Islamic terror group, that motivation alone defines this as an Islamic terror attack. It is precisely this type of attack that ISIS is calling for in the US as opposed to inviting would-be terrorists to travel to the Middle East.
And isn't it time for the full manifesto to be released? We have bits and pieces and a general idea of what it is about, but even a few words could provide more answers.