in Eu OPS, what you have to do is check your EFOB at destination regularly.
If that fuel is less than minimum diversion fuel (alternate plus final reserve) then you have to make a decision: you may divert to the destination alternate, or to an enroute alternate or you may just continue to destination (whatever you decide, you have do do it based on the circumstances at those airports and enroute) so as to land with more than the final reserve.
So it seems that if you land with less, your decision can be regarded as "erroneous". If you land with more, it still can be regarded as such.
Extra fuel gives more options, and should be function of those circumstances that affect decision to divert or continue, so you have more chances to be able to choose 'continue'.