Well, here are their respective junior stats ("so far" for Horvat). I've bolded their draft years.
Matthias
16 yrs - 1G , 1A (2 PTS) in 37 GP 0.05 PPG
17 yrs - 13G, 21A (34 PTS) in 67 GP 0.51 PPG
18 yrs - 38G, 35A (73 PTS) in 64 GP 1.14 PPG
19 yrs - 32G, 47A (79 PTS) in 53 GP 1.49 PPG
Horvat
16 yrs - 11G , 19A (30 PTS) in 64 GP 0.47 PPG
17 yrs - 33G, 28A (61 PTS) in 67 GP 0.91 PPG
18 yrs - 30G, 44A (74 PTS) in 54 GP 1.37 PPG
Bergeron
17 yrs - 23G, 50A (73 PTS) in 70 GP 1.04 PPG
As far as draft year points are concerned, Horvat had production closer to Bergeron. Matthias' PPG got "closer" in his draft +1 year but was still quite a bit lower, and he played with a guy who put up 129 points. Horvat spent his +1 year playing with the Rupert twins (both put up fewer points than Horvat). We'll have to see how things turn out with Horvat this year, but I think that saying he had a Matthias-like junior career right now is pretty inaccurate given the circumstances. That being said, Bergeron made the Bruins team right away so we'll never know how he would have done with another year of junior.