Two points:

1. Even if smaller WSD bikes typically have a steeper top tube, you can use a setback seatpost and/or move your saddle back on the rails as far as it will go to get your knee over the pedal spindle (KOPS) or even a bit behind it. I know because I have a 75-degree seat tube angle bike (Aegis Swift) and still have my KOPS with these methods.

2. Not all of us prefer WSD bikes to have a more upright position; the way we are built sometimes dictates a shorter top tube proportionally if we have a shorter upper body/arms. We might still have our handlebars lower and/or ride in the drops a lot.

IMO, the guy was a jerk and lumped all WSD bikes into one category when they can't be, any more than "all" mountain bikes, or "all" recumbents, or any other sub-segment of bikes. I'd avoid that shop on principle!

Emily