Is it normal to be able to feel the suction from a channel drain?

We heated our spa for the first time today and I noticed that I could feel more suction that I expected when putting my foot over the middle of the channel drain (the part over where the pipe enters). It’s much stronger of a suction than I expected...still able to lift my foot very easily but I expected to not be able to feel any discernible suction at all with a channel drain. Is this typical?

Also, I looked back at pictures and it seems the PB used only a single PVC pipe underneath the...

Is it normal to be able to feel the suction from a channel drain?