The firm recruits up to 90 trainees per year and have historically had about 50% of their training contracts filled by vacation scheme attendees, so I would expect a very healthy number of direct TC process.
I think this is in part where they only have around 70 VS places a year (so will never fill their TC places with vac schemers) but also where their summer scheme is for penultimate year undergraduates only, and therefore they will want to keep opportunities open for those coming to the career slightly later in their academics or career changers etc.