If you're combining it with an outline style, it works perfectly fine.
Oh and I take back what I said about it not crashing. I think my quick test on it yesterday did something odd - either that or the bug doesn't always result in a client crash.
Test #1: Works, creates the fontstring and displays "BANANAS!" at size 32 with an outline.
Lua Code:
local __T = UIParent:CreateFontString();
__T:SetFont([[Fonts\FRIZQT__.ttf]], 32, "OUTLINE");
__T:SetText("BANANAS!");
__T:SetPoint("CENTER");
Test #2: Works, same as above but with the MONOCHROME style added.
Lua Code:
local __T = UIParent:CreateFontString();
__T:SetFont([[Fonts\FRIZQT__.ttf]], 32, "MONOCHROME, OUTLINE");
__T:SetText("BANANAS!");
__T:SetPoint("CENTER");
Test #3: Crashes, no outline style specified.
Lua Code:
local __T = UIParent:CreateFontString();
__T:SetFont([[Fonts\FRIZQT__.ttf]], 32, "MONOCHROME");
__T:SetText("BANANAS!");
__T:SetPoint("CENTER");