minimum contract length 12 months, is it normal?

Hi. I’ve been out of the rental loop for 20+ years. My wife’s cousin is in London for a year to do a Master course sent by their workplace (a Government Office in Jp). They will be here for 10 months but apparently the Estate Agent they are dealing with said their landlords only accept a 12 months contract, so they have agreed to it and are willing to leave 2 months in advance. Considering how gullible japanese people can be and how slippery estate agents are, my gut feeling is that they should have pushed for a 6 months break clause, I remember I had one last time I rented. Am I right not to be too happy with their arrangement? I’m trying to baby-sit them a bit and avoid them wasting their money.