I think both camps appear to okay with term (boston at 7, Pastrnak at 8) it's just the $$$. He won't sign for 6.5, not for LTC, from what I've read coming from his agent. That's why a bridge deal makes sense. Sign for 2 yrs at 6 and then when you prove that worth, ink the LTC. Problem for Boston is that in 2 yrs, he might want more than 7 or 7.5, if he produces and I think he will.
From what Dreger reported, Boston offered 6M either for 6 or 7 yrs and Pastrnak wasn't interested. Draisaitl is also a center, which gives him a bit more clout. Dreger said Pastrnak's comparable is Tarasenko which is the number his agent seems to want.
It's a tough situation, Boston is correct to be cautious as 'star' and 'projected to be star' are 2 different things. I think he will be a star but there's nothing wrong with signing a bridge deal, helping your team, the town you play for and working for it.
And he knows that he is a big part of their offense and they will ,I think, suffer w/o him.