Could you show me where the firm has said that?
From their FAQ, it sounds to me that if you want to apply for a TC and you feel ready to apply for one, you should go for it - especially if you want to maximise your chances when it comes to the availability of places. The exception to that is if you want to apply for the winter workshop before applying for a TC.
Can I apply to a winter workshop and a training contract at the same time?
It is not necessary to have completed work experience with us to have a successful training contract application. If you already have legal work experience and/or you feel ready to apply directly for a training contract, we would encourage you to do so. If you would still like to apply for the winter workshop before applying for a training contract, please bear in mind that training contract interviews will be scheduled and offers will be made on a rolling basis. We are therefore unable to guarantee the availability of places as we progress with these interviews.
I'd flag that I don't have any insider knowledge though, so I may be wrong on this.
it was sent in the email after we applied.