Describe the bug

Here's a self-contained reproducer:

import ROOT

ROOT.RDataFrame(10).Define("x", "int(rdfentry_)").Snapshot("t", "f.root")

f = ROOT.TFile("f.root")
t = f.Get("t")
reader = ROOT.TTreeReader(t)
age = ROOT.TTreeReaderValue['int'](reader, "x")
staff_list = []
for entry in reader:
    print(age.Get()[0])

This prints

1
2
3
4
5
6
7
8
9
9

instead of

0
1
2
3
4
5
6
7
8
9

Expected behavior

Either Python iteration should be disabled (in favor of while reader.Next(), which works as expected) or it should produce the same results as the while reader.Next() loop.

Additional context

First reported at https://root-forum.cern.ch/t/ttreereader-vs-rdataframe-vs-branches-to-read-ttree/44785