I'm not familiar with PETT.That is is true. With the layer having a round profile on top you get less contact between layers and less strength. I traded off strength for maximum clarity which is ok in a vase.
If I was wanting a stronger print I would use a lower layer height and more layers. But the plastic would have a cloudy look to it.
Another factor is the plastic being used, since PETT is "sticky" when hot, you have a higher layer height and still get bonding of the layers.
A nice thing about 3D printing is you never run of things to learn due to all of the different options that are available.