If a sprayer isn't blending the colour, especially silver, then they're not doing their job properly. Very rarely will we paint something like a door or a wing and say, "we probably didn't need to blend that" but it's NEVER worth the risk. EVER. Way to expensive to sort if the shade is even SLIGHTLY out.
Doing a spoiler or a mirror cap etc is a different story obviously, but even with colour swabs, the car could have been painted before. Even a couple of grams mixed wrong will throw the colour completely off. Trust me. Wings and bumpers will look horrendous and stick out like a sore thumb is the shade is even a gram or two out. Maybe you never picked up on it, working with paint for just a summer, but I'd cringe and NEVER give someone their car bacl like that.
JCC, spot on mate. We're exactly the same. The people that insist they just want one panel done are usually the tw*ts that expect it to be spot on.
Stevie, good man for getting it blended. You'll have nothing to worry about so long as they're pretty good.