Here's my take on what's being said in these articles and off-season comments, in general. I think what they're saying is absolutely true. I think these guys are getting stronger and faster. I think they're trying to do more than they did last year.
Let's look at if from a slightly different perspective. ZL was not the starter last year. That means the starter last year (in this case David Sims) was better than he was [in theory]. To be as good as the starter was last year, ZL would need to improve his performance, i.e. get stronger and faster 0r understand the offense better or block better, etc. If these kids aren't improving, then the skill level and perfomance of the kids rising to replace last year's starters who have moved on will be behind last year's starters. That would be very, very bad. We want last year's back-ups to improve AT LEAST to the level of last year's starters so that we're not moving backwards. The two spots most people are worrying about this are WDE (Attaochu) and DB (Thomas).
So, I expect these kids to continue to improve, grow, mature over an off-season. That's how you reload, not rebuild.