Proj applying unit conversions twice for altitudes in some compound coordinate systems?

I noticed that Proj 6.2.0 seems to apply unit conversion from feet to
meters twice when transforming from the following coordinate system to
EPSG:4326:

  COMPD_CS["unknown",PROJCS["unknown",GEOGCS["unnamed
ellipse",DATUM["unknown",SPHEROID["unnamed",6378137,298.257222932961],TOWGS84[0,0,0,0,0,0,0]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",42.5017284],PARAMETER["central_meridian",-87.94173071],PARAMETER["scale_factor",1.00002879],PARAMETER["false_easting",2555070.71005833],PARAMETER["false_northing",189709.351551667],UNIT["US
survey
foot",0.304800609601219,AUTHORITY["EPSG","9003"]],AXIS["Easting",EAST],AXIS["Northing",NORTH]],VERT_CS["unknown",VERT_DATUM["unknown",2005],UNIT["US
survey foot",0.304800609601219,AUTHORITY["EPSG","9003"]],AXIS["Up",UP]]]

Note that this coordinate system is compound and has both a horizontal
component and a vertical component in feet. Running cs2cs 6.2.0, I get
something like:

  $cs2cs 'COMPD_CS["unknown",PROJCS["unknown",GEOGCS["unnamed
ellipse",DATUM["unknown",SPHEROID["unnamed",6378137,298.257222932961],TOWGS84[0,0,0,0,0,0,0]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",42.5017284],PARAMETER["central_meridian",-87.94173071],PARAMETER["scale_factor",1.00002879],PARAMETER["false_easting",2555070.71005833],PARAMETER["false_northing",189709.351551667],UNIT["US
survey
foot",0.304800609601219,AUTHORITY["EPSG","9003"]],AXIS["Easting",EAST],AXIS["Northing",NORTH]],VERT_CS["unknown",VERT_DATUM["unknown",2005],UNIT["US
survey foot",0.304800609601219,AUTHORITY["EPSG","9003"]],AXIS["Up",UP]]]'
+to +init=epsg:4326 <<EOF
0.0 0.0 682.1900
EOF

  97d16'41.701"W 41d36'0.332"N 63.378

Note that 63.378 ~= 682.1900 * 0.304800609601219 * 0.304800609601219. For
our use case we're expecting something like 207.932 ~= 682.1900 *
0.304800609601219 instead.

Is the current PRoj 6.2.0 behavior expected?

Thanks!
Gary

_______________________________________________
PROJ mailing list
[email protected]
https://lists.osgeo.org/mailman/listinfo/proj