Error: "SetPoint would result in anchor family connection"

[LudiusMaximus]

When I do

_G.FramerateLabel:ClearAllPoints()
_G.FramerateLabel:SetPoint("TOPLEFT", "UIParent", "TOPLEFT")

I get (since 8.2) the following error:

Message: Interface\FrameXML\UIParent.lua:2356: Action[SetPoint] failed because[SetPoint would result in anchor family connection]: attempted from: FramerateLabel:SetPoint

But the effect is exactly what I want: FramerateLabel moves to the top left corner of UIParent.

So what is the meaning of this error?
And is there a way to achieve what I want without causing an error?