Defending the SO, in choirs the rule is "the right note at the wrong time is a wrong note". I've had this drummed into me in the singing group I'm in now. I'd also hate it if our church organist slowed up to get a difficult chord.

I think it comes naturally to slow down & find that chord, but one does need to work on both & be able to play on through. Thinking back to typing lessons, does anyone remember the speed drills where you typed as fast as possible, sometimes even with a rhythm playing, without reference to mistakes? Then you slow down to work on accuracy, but by pushing through faster than you wanted, you did go faster when you slowed down.

I can't claim competency on an instrument but have been trying to learn pennywhistle. I try to play through at whatever tempo I've selected. If there's are notes I don't get, instead of stopping or slowing for a note or two, I try to back up & slow down a whole passage. Play the whole group of measures at a slower speed, but with all in proper rhythm to learn it, then speed it up to tempo.