[PROJ] proj8 and NAD27 <-> NAD83 transform

[Kirk Waters - NOAA Federal]

Dear proj list,
I'm having a bit of trouble with proj and I'm hoping someone can tell me
where I've gone wrong. For context, my primary issue is converting a raster
from NAD83 state plane to NAD27 state plane using GDAL, which uses proj
under the hood. It looks like it's proj that is causing me problems. I used
conda to install a fresh environment with proj8 and proj-data on a RHEL7
machine.
Here's the conversion that I think is giving the wrong answers (EPSG 6570
is NAD83(2011) South Carolina State Plane (ft) and EPSG 32033 is NAD27
South Carolina South):

cs2cs EPSG:6570 EPSG:32033 << EOF
2320610.000 353815.000 0
EOF

which returns:
2320626.52      353751.41 0.00

Using the NGS NCAT online program, that should be:
2320568.869   353687.842

I did the transform in parts and found that the issue is in the reference
frame transform between NAD83(2011) lat lon and NAD27 lat lon, where no
change happens, but it should. That is:
cs2cs EPSG:6318 EPSG:4267
with inputs of
32d48'4.701"N   79d57'23.546"W 0.000
has outputs of
32d48'4.701"N   79d57'23.546"W 0.000

If I use NAD83 (EPSG 4269) instead of NAD83(2011), things look right and I
get output of:
32d48'4.066"N   79d57'24.227"W 0.000

Trying to change from NAD83(2011) to NAD83 (EPSG 6318 to 4269) gives no
change, so I'm assuming PROJ doesn't know that transform. I'm guessing that
because it doesn't know that transform, it can't figure out that it should
do the NAD83 to NAD27 part, so instead of being a couple meters off, it's
off by 50 meters or so. If I do the transforms in parts, SP83 to
NAD83(2011), NAD83(2011) to NAD83, NAD83 to NAD27, NAD27 to SP27, I get the
right answer within the couple meters due to the missing transform.

Is the transform from NAD83(2011) to NAD83 something I just missed
installing? Without it, it looks like my GDAL process will be painful. Is
there a better way to handle it?

Kirk Waters, PhD                     | NOAA Office for Coastal Management
Applied Sciences Program      | 2234 South Hobson Ave
843-740-1227 (empty office)   | Charleston, SC 29405
843-324-2203 (cell during COVID)
coast.noaa.gov/digitalcoast
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/proj/attachments/20210602/e9f066c7/attachment.html>