Yes, on Bering thermals currently, the only way to increase the magnification of the PIP is to also increase the magnification of the main window.
Super Yoter has 1x, 2x, 3x, and 4x digital zoom which translates to 3x, 6x, 9x, and 12x main window magnification. The corresponding PIP values are 6x, 12x, 18x, and 24x. It is always twice the main magnification. I realize Pulsar does their PIP very different, and allows you to zoom either or both. I know many people like to run it as you mentioned with the main window at base mag and PIP zoomed way in. That would not be for me, but that is OK.