Surveyors just love to survey everything. Sort of like the way architects love to dream and doodle.

So tell me about elevation....

Are all these topo maps and surveys gonna be wrong when the sea level rises a foot?

Hehe.
Probably not before the National Geodetic Survey (NGS) screws around and moves the center of the Earth in their ECEF (Earth Centered-Earth Fixed) program....again.

THE DATUM has a date as of 1927 for the standard stuff

then they were switching to 1983 when I quit in 2000
they do not adjust it very often

https://www.usgs.gov/faqs/how-large-north-american-datum-1927-nad-27-nad-83-shift

it is just numbers avg over a time
and tides vary by air pressure wind direction also