There must be more to it than that. Who owns these HSTs? The first one was transferred to East Coast years and years ago. It's an extension of this process that there are three now rather than one, and I personally would be asking serious questions about why, but still. I really hope EMT can find something else to boost capacity to and from Skegness. However I would make the point that before last year it might have been difficult to predict the rise of a place like Skegness in terms of rail travel. It's also very seasonal and seems only to affect Friday, Saturday, Sunday flows. By contrast traffic between Leeds and London is regular, growing steadily and is a heavy flow every day of the week, all year round.
We can hope that by next summer there will be plenty of HST availability as a result of new stock at east coast... hopefully...