I’m quite sure there is no such a thing as an oscilloscope probe with a 50-ohm resistor at the oscilloscope end. The 50 ohm termination is only used for transmission lines (coaxial cables with 50 ohm characteristic impedance, in most cases that involve oscilloscopes), to prevent/minimize reflections that create artifacts on the screen. There are quite a few old (but still amazingly enlightening) Tektronix YouTube videos that address the issue. “The art of electronics” has an excellent chapter (or appendix, IIRC) on transmission lines.
Or maybe I don’t understand your question, case in which I apologize….