Sometimes the Window Switcher shows Apps Multiple times.
It does depend on what app is active so for example if I trigger it in:
Illustrator:
( with 1 window and 2 tabs open )
Indesign:
( with 1 window and 3 tabs open )
Adobe usually handles windows a bit different, that might be causing it. But I did get the same thing with other apps as well, though more rarely. Once for example I had about 20 BetterTouchTools in the Window Switcher.
Latest BTT version: 3.086
Mojave 10.14.3