I'm beginning to get it now.
You do ring your sailmaker and get him to come down and go for a sail
in a variety of conditions so he can see jus how you sail and design a
nice set of cruising sails tailored to your particular way of sailing.
He makes all the right noises, drinks your beer, makes a few notes,
accepts your offer to dinner, then delivers the sails in a couple of
weeks.
Of course he goes for a sail, drinks your beers, makes some more
notes, accepts your offer to dinner and humbly accepts your praise on
how well the sails suit your boat and driving style.

Thing is Billy, the notes he was taking were so he'd remember your
comments.
He didn't want to forget one single word you said when he gets back to
the loft and the whole bunch sit around laughing their heads off at
the sucker they just reeled in!!!
Then they'll get back to the computer and bring up the templates for
the next set of "custom" sails, lay the cloth out on the table, turn
on the air and watch the plotter mark it up.

I made my sailmaker come down to my boat three times and we had many phone
calls and emails to go over details. He measured my rig completely and we
discussed the type of sailing I do. When the sails were done he fitted them
and had to take them back because the reefing pulls were on the wrong side for
the Dutchman. We went over the ways in which my sails differed from the stock
sails delivered on an IP, a dedicated cruising boat. Details in a cruising
sail matter also, and you gotta make sure you get what you want.