The InputStream knows nothing about encodings

I agree with this. but when it comes to ReaderInputStream which is a converter from Reader to InputStream, it should consider encoding problem.
I referred to the implemation of commons-io ReaderInputStream.

I did the same test on the Oracle database, ClobProxy didn't be used.
(Maybe the Connection in Oracle driver implements createClob?)

I think this happens in those drivers that use ClobProxy::getAsciiStream.