Is it normal when BLEU score on filtered data by length is greater than BLEU score on whole data
The original BLEU scores 25.9 and 25.7 are very close, there might not even be any significant difference. It's totally possible that model B performs better than model A on the filtered data only by chance. It's also possible that model B actually performs better than model A on shorter sentences. And finally it's worth noting that BLEU score is based on the number of n-grams in common, so it's likely to be affected by the length of sentences independently from the model being tested.

Conclusion: based on the information provided, this difference seems perfectly reasonable.