corduroy suit jacket alterations - true or false?

Picked up a corduroy suit at Nordstrom Rack today, and when I asked the tailor if she would shorten the sleeves a touch she claimed it would not be a good idea, because with corduroy 1) it would be hard to refinish it to get the same look after the alteration, 2) she would have to redo the (fake) button holes (further affecting the finish of the fabric) and 3) corduroy suits will shrink a bit after the first dry clean, anyway.

I couldn't figure out if she was giving me good advice or just a salaried employee who was trying to avoid extra work.

The sleeves are actually an acceptable length, but I was looking for maybe 1/8th of an inch shorter-- not enough for me to argue with her about it. I can still change my mind when I pick up the suit (I wasn't wearing a dress shirt, so I will do so when I pick it up, and re-evaluate then).

So, was she spinning a yarn, or is she legit?

I don't think she is entirely correct, but corduroy may be a little bit harder to work with depending on
the width of the wale.
For one eiighth of an inch I wouldn't worry though. The sleeves are going wrinkle a bit
and will ride up at least an eighth of an inch with wear anyway. That's what corduroy is
supposed to do.

Don't know why it wouldn't look the same. Removing the fake buttonholes will leave a mark in the cloth that won't come out but you wouldn't have to remove them if you only shorten the sleeve by 1/8", especially if you only shorten the front and not fool with the vent. Shortening a corduroy jacket sleeve 1/8 seems odd. The sleeve will shift from wearing it. Wear it a few times and see if it is necessary.