Yes, you missed to configure the font for hex/column mode which of course can be the same font with same font size as for normal text editing mode if the font is a fixed width font.
With using the ribbon interface click on ribbon tab View on triangle below Fonts on left side and click in opened popup menu on Set hex/column mode font. Such a menu item exists also in menu View on using toolbar/menu mode with contemporary or traditional menus.
There are different settings for normal text editing mode and hex/column mode as in normal text editing mode a proportional font can be also used while in hex mode and in column mode the font must be a fixed width font. Programmers use usually in all modes a monospaced font, best a fixed pitch font on using also font styles bold and italic. For example HTML writers use a proportional font in normal text editing mode and need rarely the column mode and most likely never the hex editing mode.