That's a bullshit explanation of cultural appropriation and the person you heard it from is an idiot. Actual cultural appropriation is when you take something from another culture and either erase or overwrite its origin, so the original culture in its original form becomes forgotten.

For example, when white artists re-recorded songs from black artists and specifically removed them from the credits and claimed them as their own, that was cultural appropriation. When movie studios chopped up Indian culture and presented it in a completely distorted and inaccurate light, so much so that the original meanings were lost, that was cultural appropriation.

Simply being a participant in someone else's cultural celebration is not cultural appropriation.