Pajo, I think who ever told you that was either pulling your leg, or excusing laziness.
The chain-stitch machine invented around the 1830s did mimic the crappy stitch you see on modern coal-sacks. It's an easy stitch to mimic, but it has the problem that it's really easy to unravel. Pretty useless, really. The 1850's "Singer shuttle" machine didn't mimic any human stitch, for obvious reasons - it uses one thread that just goes up and down in a straight line, and a second thread that loops around the first. It's a stitch that would be very hard to do for a human - more like crochet - and it's really not that good unless the tension is both high and constant - making it useless for loose materials or wools. The modern rotary hook machines (developed in the 1860s!) have a stitch that's very similar, so not really worth discussing.
Check any book on medieval clothing design; there are literally dozens of different stitches, each has it's own place. They all give differing decorative styles, depending on how they are used. Check out
this photo of a tunic made on a 14thC Greenland find - there are four photos in that sequence. There are different stitches for the neck, underarm, hems, shoulder/body joins and the backs of the gores. You could try replicate this with modern stitches or a machine, but it would look completely different. I've a great industrial machine that'll stitch 2.4mm leather together. But I wouldn't use it for making reenactment clothes, unless they weren't meant to be seen closer than 15 metres away...
John