It's not a matter of trusting the photos, but simply a matter of standard dimensions.

Even among the most extreme upright bicycle designs bottom bracket heights don't vary by more than a couple inches and crank arm lengths don't vary by more than an inch. So no matter which bike we're discussing (no matter which manufacturer, model, or type) the crank arm in the 12 o'clock position will always be the same height plus or minus an inch or two at most.

So we're not talking about trying to eyeball minor differences from the photo or compare sizes between photos, but rather simply making the blatantly obvious observation of whether the frame tube is close to the pedal in the 12 o'clock position or not. This requires no more trust in the photo than trusting whether the saddle is of roughly equal height with the handlebars. The answer unquestionable and unmistakable.