Console Virtual Terminal Sequence to Clear Console Fails in Main Buffer - windows

Question

Win10, VS 2019 v16.11.5
Below is the minimum code to output some text to a console in Win10 and attempt to clear the buffer contents (a screen clear, if you will). When I use the default buffer, the text is merely scrolled up. When I use the alternate buffer, the same terminal sequence performs as expected.
The first two dozen lines or so (until the window title change) are preamble to get the console handle and set the correct output mode for terminal processing. Problem code commences after this.
Why doesn't this work in the main buffer?
Reference: https://learn.microsoft.com/en-us/windows/console/console-virtual-terminal-sequences
#include <iostream>
#include <windows.h>
#include <conio.h>
#define ESC "\x1b"
#define CSI "\x1b["
int main()
{
// Get the handle for standard out
HANDLE hStdout = GetStdHandle(STD_OUTPUT_HANDLE);
// If the handle is invalid, exit
if (hStdout == INVALID_HANDLE_VALUE)
{
std::cout << "GetStdHandle failed with " << GetLastError() << "\n";
return 1;
}
std::cout << "Console Handle valid";
DWORD dwMode = 0;
if (!GetConsoleMode(hStdout, &dwMode))
{
std::cout << "GetConsoleMode call failed with " << GetLastError() << "\n";
return false;
}
// see https://learn.microsoft.com/en-us/windows/console/setconsolemode.
// Don't reset, if already set.
if (!(dwMode & ENABLE_VIRTUAL_TERMINAL_PROCESSING))
{
dwMode |= ENABLE_VIRTUAL_TERMINAL_PROCESSING;
if (!SetConsoleMode(hStdout, dwMode)) // set dwMode
{
std::cout << "SetConsoleMode failed with " << GetLastError() << "\n";
return 1;
}
}
// Change the window title
printf(ESC "]0;Console Screen Exploration\x1b\x5c");
// Add another line of text
std::cout << "\nIn main buffer by default\n";
char wait = _getch();
// Cursor to 1,1 and clear console but all it seems to do is scroll up??
// see https://learn.microsoft.com/en-us/windows/console/console-virtual-terminal-sequences#text-modification
printf(CSI "1;1H");
printf(CSI "2J");
wait = _getch();
// Whereas, if I perform these operations on the alternate buffer, it works
// Set alternate buffer
// see https://learn.microsoft.com/en-us/windows/console/console-virtual-terminal-sequences#alternate-screen-buffer
printf(CSI "?1049h");
std::cout << "Alternate Buffer\nNow clear console";
wait = _getch();
// Move to 1,1, then clear screen
printf(CSI "1;1H");
printf(CSI "2J");
wait = _getch();
// back to main buffer
printf(CSI "?1049l");
std::cout << "Back to main buffer";
}