You're buddies are probably mistaken. I believe a straight can be made every bit as sharp as any other instrument. Mr. Parker could give us a good scientific explanation for this but I'll try on more laymen's terms.
Search for a link to the Verhoven paper. Professor Verhoven did a series of experiments on sharpness etc. Everything maxes out at a certain level (@4k). After that it's all about how smooth the edges of the bevel are. Modern production razors user teflon coatings and I suspect scalpels might as well. But whatever the circumstance the bottom line is I think straights can be made every bit as sharp as anything else.
Best Regards,
EL