Foo. Bar.
Foo. Bar.
Foo. Bar.
NaN. Bar.
NaN. Bar.
NaN. Bar.
with texinfo 5.1.dfsg.1-4 (I've removed the blank lines).
What are you reporting? The above looks correct to me; the previous
behavior (of preserving intersentence spacing in some situations) was a
deficiency, although admittedly a longstanding one.
karl