"..The problem arises in positions like Dia. 3-7. Only neutral points are left, the number of neutral points is even, the black group at the bottom has lost its outside liberties, and the safety of this group is uncertain. Suppose it is Black's turn. Even if Black plays 'a' to remove the danger, he can still get one of the two neutral points. Under area rules, that is, he can make a free reinforcing move at 'a.' He does not need to verify whether it is actually necessary..." -- Section 3.5 "The disadvantage of Area Rules",
On the Rules of Go, Ikeda Toshio
After (1) White assumes black is skilled enough to avert the invasion and occupies the last dame.
Territory+Prisoners Score W30 B31 Area Score W60 B61
Ikeda's Rule Black passes first W60 B61
Button Go Black passes first +0.5 Black W60 B61.5
Black unnecessarily reinforces its territory.
Territory+Prisoners Score W30 B30
Area Score W60 B61
Ikeda's Rule White passes first +1 white W61 B61
Button Go White passes first +0.5 white W60.5 B61
Obviously it loses, yet by keeping sente it prevents black from grabbing the last dame.
Territory+Prisoners Score W35 B36
Area Score W60 B61
Ikeda's Rule Black passes first W60 B61
Button Go Black passes first +0.5 Black W60 B61.5
White's IQ is getting worse, this time it not only invades but also loses sente by performing Baka no Itte. It is punished by losing both dame.
Territory+Prisoners Score W30 B32
Area Score W59 B62
Ikeda's Rule White passes first +1 white W60 B62
Button Go White passes first +0.5 white W59.5 B62