The point is, he can probably avoid what has happened in the picture and avoid buying cranks by buying a longer BB.
Get it?
Here is the proof -
Onza t-bird crankset - £40
Trialtech Race Square Taper BB, £12
So, if he's wanting the t-bird cranks, he must have a square taper BB already. So, he must have square taper cranks already. Therefore, if he spends £12 on a looooooooong BB that will cause his current cranks to clear the frame, he's avoided spending another £28 on cranks that might not necessarily solve the problem.
I win.