I think it is true that the Celtics are "soft" at least in regards to having bigs that can rebound and defend the rim. When Tatum is your starting PF, that is going to be a problem.
I don't think the 10 point thing has any relevance to this though. Our bench is adequate now, if the team ever gets reasonably healthy. I assume Thompson is a starter so our first tier bench is:
Pritchard
Fournier
Parker
RWilliams
That is not horrible, and the second tier bench is GWilliams, Ojeleye, Kornet, Langford, Nesmith, and Edwards. Again, as second tier bench players, these are all serviceable.
The problem is that due to injuries, some of our second tier bench players end up starting. It is also an issue that two of our first tier bench are new players and not really fully integrated but if we have exactly these players for our bench next season, I don't think it will be a weakness.
And if we are able to add a legit starting level PF to the team, then things look even better in terms of depth.