The MatthewsFolbigg program is not a typical summer clerkship program.
In fact, it seems like an initiative they've developed themselves to recruit young lawyers, so it's not part of the "official" program run with the unis. Hence the strange timing.
If I were going for a larger firm, i would be minded to stay away, lest it clashes with a (real) summer clerkship later in the year. That said, all experience is good experience. To be perfectly honest I think it's slightly misleading calling these programs clerkships.