Marker type for acgh is 'Chromosomal'

Not 'Chromosomal Region'. Apparently.
Check for extra assays in row group & error out

If allowMissingAssays was true, this error condition would trigger the
code path for a non-obvious exception further down the road. To make
matters worse, when creating the message for this exception, another
exception would be raised, which would further complicate
troubleshooting.