Not using native Win32 HWND based controls does not imply UWP. Virtually every program that was made for Windows XP and later does not use native Win32 controls; this includes “outdated” frameworks like WinForms.
X11 and Win32 UI are actually fairly similar in this respect.
Actually the VCL[1], shipped with Delphi, does to a large extent use the native Win32 controls. They've added some quality of life stuff on top of them, but the TEdit component[2] is a wrapper around the Win32 edit control etc.
Delphi is not so popular these days, but there still is a fair share of Delphi programs running.
X11 and Win32 UI are actually fairly similar in this respect.