xdm, pager (less) ion-manual page viewing

Hello, what is the difference between starting X with xdm and with startx?  When
i start X with the startx command, the pager which displays the manuals works as
it should, but when i start ion with xdm the pager (less) exits after it gets to
the last line, which is annoying if the page is smaller then 1 screen, because i
can't read that fast.

My .xsession and .xinit both end with these lines:
/usr/X11R6/bin/ion3 &
xmms &
xterm -name main &
exec /usr/X11R6/bin/xterm -name login

I don't have any less-environment or config options on and couldn't find anywhere
if xdm changes some of those. So i don't understand why the pager behaves differently
after i start X with xdm.

-greetings, jurjen

note: with pager i mean the pager that gets opened with the mod_query.query_man()