In the maxpoints conversion dialog listener (which handles the value conversions based on the maxpoints entered by the user), code that attempts to detect the type of data (letter or number) that is imported for an item is not correct and the result is that all imported values are assumed to be letters and so if importing nummbers into LETTERS gradebooks, conversions (appear) to not be done.
This regular expression is matching all values and the variable is set to TRUE
Later that boolean assumeLetterImport (which is currently always TRUE) is used in conjunction with importingIntoLetters (TRUE if the current GradeType == LETTERS) to decide whether to do the actual value conversions.
The effect of this logic is that conversions will only take place on values if the import is into a GradeType that is NOT 'LETTERS'
This suggests that number-valued imports into LETTERS gradebooks is not working
If true, the result is no different than what happens in 1.7.0