Uncomfortable position...

That changes your pedal action though since you're moved further behind the bb spindle.
It can provide increased glute use which is good but it can also cause you to hunch your lower back and this will be painful on longer rides and not good long term.
There's nothing wrong with spacers or flipped stems and bike-fitting for aesthetic reasons is silly.

Partially true. The only impact on your muscle recruitment is the change in hip angle (i.e. your glutes don't know where the BB is!). Thus you'll only get a hunched lower back if you're tight in your hips, and you'll feel this pretty quickly as lower back pain. In which case, shift forward and/or bring the bars closer.

Given the option of a) higher bars and a more forward saddle b) lower bars and a more rearward saddle, b) is always going to be a winner considering both aerodynamics and muscle recuitment, assuming you can rotate your hips sufficiently.

Like everything it's a balancing act!

It's just good to be aware of the various options - saddle fore-aft position is normally a complete afterthought. I struggled for years until I realised I needed to get my saddle right back and couldn't get on with any frame (from a a comfort point of view) with a steeper than 73degree seat-tube angle. I can quite imagine that, what with the trend for steep track frames, a lot of people are riding in a position that is really compromised in this respect.

Courant (who also runs spacers and flipped stem to get his position right!)