basic_filebuf::setbuf does only work with binary mode

I observe that basic_filebuf::setbuf only actually respects the manual buffering (using the provided buffer), if std::ios::binary is set, otherwise a call to setbuf is ignored. For testing this I captured a WPA trace of the following Code, with and without std::ios::binary set and looked at the "Storage > Size by Process, Stack for Read/Write" report for the test executable. Sadly we don't have strace on Windows ;) ... so the repro and testing is a bit more involved

#include <fstream>

int main() {
  size_t constexpr buf_size = 1024 * 1024;
  auto buf = std::make_unique<char[]>(buf_size);
  std::ofstream test("test.txt", std::ios::binary);
  test.rdbuf()->pubsetbuf(buf.get(), buf_size);
  for (int i = 0; i < 10 * 1024 * 1024; ++i) {
    test << "test";
  }
}

with std::ios::binary:

47 Writes/Reads of 1MiB each on Avg. (this is what one would hope/expect)

without std::ios::binary:

9.777 Writes/Reads of ~5KiB each on Avg. (this one not)

Expected behavior
I would expect basic_filebuf::setbuf to sets the buffering in any case.

STL version

Microsoft Visual Studio Community 2022 (64-bit) - Current
Version 17.1.3

Start by building the supplied C++ reproducer with and without std::ios::binary, then compare the WPA Storage > Size by Process, Stack for Read/Write results. Investigate basic_filebuf::setbuf behavior in the MSVC STL; done when the provided buffer is respected in text mode as well as binary mode.