pibeti

*pibeti is an often discuss word because of the *b where a *p is
expected. However that's not the point of this posting. This is a
reduplicated form of *po:. According to the laryngeal theory this
should be reconstructed as *peH3. The reduplicated form would then be
*pipH3-eti. However this should result in **pipoti. Again, ignoring
the issue of *b, why do we have an *e attested instead of *o?

Must we reconstruct it as *poH1 instead? If so, what is the
explanation for the o-grade.