[ooo-build] Strange installation directory layout in 3.1.x

[espinosa_cz]

Please, can someone comment on the linux installation directory layout.
Why there are two separate directories under /opt ?
/opt/openoffice.org/ - 284.9 MiB
/opt/openoffice.org3 - only 1.4 MiB but it contains the main binary - 
/opt/openoffice.org3/program/soffice
I tried to find answer in wiki or phorums.
Is it because some I/O optimalisations or rather version management?
Was this layout introduced in ooo-build, is it also present in vanilla 
build?
Does Suse build uses the same layout?
I'm asking just from curiosity.
Thank you
Jan