No. Just to add to what John wrote -
You ‘weren’t feeling’ the resistance associated with an increase in gradient, that’s true. Because, in an ERG workout, you wouldn’t be able to sustain exactly 205W for 15 min if hill simulation was still active w/o shifting gears - and even then, it would be challenging to do so.
If you were passing people on climbs any more than you typically do, it’s because they were, coincidentally, riding slower than you - not because ERG made you faster.
If you pay close attention to your speed (or go back now and review your workout data on Strava), you’ll see that your speed decreases as you go uphill (and increases as you descend) even though your power output is ‘flat’ at 205W the entire time.