value returned by innodb fulltext searches differs from myisam one (no replies)

In short, myisam returns a value that is calculated over the words frequency, while innodb seems to ignore it and just returns the same value for the whole resultset (sorry for the lack of proper terminology)

for example, searching "aaaa":


this is myisam:


fulltextIndex | ftNatLangResult
--------------------------------------
aaaa bbbb ccccc | 3.6000000 (higher word frequency)
aaaa bbbb ccccc dddd | 3.1000000


this is innodb:


fulltextIndex | ftNatLangResult
--------------------------------------
aaaa bbbb ccccc | 3.3000000
aaaa bbbb ccccc dddd | 3.3000000 (no difference with the above)


is there a way to fix this behavior? i checked the documentation but i couldn't find anything that mention this difference

thanks in advance for the help