Presented as a literal thing, but is really figurative. What I mean is, often you don’t have the data to actually plot/PCA/whatever technique the seasonality, maybe you only have 2 years of data for example. But it dips in October and you have no idea why so you just say “Q4 tends to be a low season for this product” or something equally dubious, with no further analysis or hope of same
Just because something happens on a yearly cadence doesn't mean that "seasonality" is a good reasoning. It's just restating that it happens on a yearly cadence, it doesn't actually explain why it happens.
Is this a literal thing or figurative thing? Because it should be very easy to see the seasons if you have a few years of data.
I just attribute all the data I don't like to noise :-)