Yes, tolerances and other things need to be discussed. STEP files can technically convey most of these things, but in practice most MCAD software cannot output these details to STEP files, and most machine shops won't check these details anyway. Both parties tend to revert to 2D PDF drawings to agree on details, and more importantly figure out whose fault it is in case of a mistake in production.

ECAD is way more standardized than MCAD for information sharing and version control, and at least has industry standard best practices. MCAD is still a wild west, with mostly proprietary tools used for version control (several thousand dollars per user per year) with no hope of interoperability. And each vendor that offers automated quoting uses a proprietary system, with a lot of manual inputs.

Granted, mechanical parts can be much more complex and it's easy to make unmanufacturable parts in MCAD, whereas ECAD is basically a stack of 2D layers. But still, as a mechanical engineer I am amazed at how easy it is to order a PCB or even an assembled PCB compared to ordering the simplest machined part.