This is probably more complicated with Tahoma because it has different versions including bold, properly flagged as bold with weight 700. Windows probably doesn't embolden fonts properly flagged as bold, as far as my interactive test goes. However, the degree of emboldenment does depend on the original font weight and requested font weight when synthetic emboldenment is performed. I am attaching an interactive test program I used for testing the appearence with various fonts. With the wine_heavy.ttf added to tests with this MR dropped into the run directory (as well as with the font from the game) it clearly shows how the text with higher requested weight is bolder than FW_BOLD (700) (look at first 'A' character displayed as | from test font, the rest is substituted from some other font on Windows).
[ttf2.c](/uploads/8d9ef1340da25f4fbec0f2755c20874d/ttf2.c)