Samll amounts of Dextrin Powder inhibit bittering by Hops?

I was using Beercalculus software and found what looks like an anomaly. According to the software, if I add just 2 oz of dextrin powder during the boil, the hops are inhibited and the calculated IBU's drops off severely. I know that malts inhibit the bittering, but I do a late addition with my extracts to address this and caramelization concerns. I am fairly new to brewing (have brewed 11 batches so far) and have always added dextrin at the beginning of the boil because the first book I read said to do so for a better head and retention - it appears to have worked well (my beers have all had a strong head and retention). If anyone knows the answer to this question, I figured it would be someone here. Otherwise, I think I found a bug in the new Beercalculus software.

Something is wrong with the program. Malts don't "inhibit" bittering. Higher gravity boils, like extract partial boils, yield less IBU extraction percentage so you do need slightly more hops in a partial boil compared to a full boil of the same recipe to get the same amount of bittering. However, 2 oz of maltodextrin added to a recipe will not make a significant difference.

I'll second the "it's a bug".