Thanks for answering ! You're probably right about this point, but I'm feeling people could also way more easily stall games if you allow 15 free days banked, which end up being 15x6=90 free days banked per player per template ; compared to 50-70 days max that players have to spend on their own yearly vacations
Three times 70 days of vacations per player equals 210 days of stalling, at which point you might even get new vacations because the new year starts. If you take it to the extremes and want to stall intentionally as a clan, six members could stall CL forever (before we disqualify them obviously). The 15-day bank rule ensures this doesn't happen.