doc minimum requirements

Readme.md

@@ -9,7 +9,8 @@ Matlab or GNU Octave users coming from other languages often notice the missing
 These system, filesystem, and HDF5 / HDF4 / NetCDF functions are useful across several of our own and others projects.
 
 Matlab ≥ R2021a has full functionality.
-Older versions of Matlab work back to about R2017b.
+Matlab R2019b is the minimum required due to use of
+[arguments](https://www.mathworks.com/help/matlab/ref/arguments.html) syntax.
 If using GNU Octave, the minimum version is 6.0.
 
 Self-tests can be run from that matlab-stdlib/ directory:
@@ -20,7 +21,8 @@ buildtool
 
 [API Documentation](https://geospace-code.github.io/matlab-stdlib)
 
-Many Matlab-Stdlib functions use the factory JRE in Matlab or GNU Octave, and have been tested with JVM versions 8 and 17.
+Many Matlab-Stdlib functions use the factory JRE in Matlab or GNU Octave, and have been tested with JVM versions 8 and 17 and newer.
+Most Matlab-stdlib filesystem functions do not require Java.
 For reference, we further
 [discuss Java implementation details](./Readme_java.md).