No, it's the 3rd tube, and it's a 12AT7, not a 12AX7. The PI is V4 and is also a 12AT7. You can change the plate load resistors on the PI and use a 12AX7 if you want to, but the T is historically correct for the PI and sounds good with this circuit.
Strangely enough, the buffered loop is designed for a 12AX7 (100K plates), but works real nice with the 12AT7, more current draw, I prefer T's in loop duty. Maybe someone else can explain why that might be?
I just checked mine out with two Avatar 1x12s loaded with Altec 417Bs, man you cannot beat that old school Alnico tone with this amp! 3" voice coils help too!