They're referring to multiple WMT applications.
Yes, but it’s ambiguous.
It appears their trying to make it sound that your not permitted to apply if you have any other active applications.
Railway recruitment, especially driver recruitment seems to be a one way street in terms of how HR departments treat potential employees. The Virgin EC scandal where dozens of people were taken right through the process only to be dropped like hot rocks is typical of the contempt they hold you in.
Talent Pools are the recruitment version of Zero hour contracts, keeping you semi commited to something which may well never happen.
We all know there are literally thousands of people who will sell their nan to get a trainee job, HR know this full well so they can literally treat you how they wish with zero comeback.