If I was an employee who was effectively being seconded to another organisation, I’d be looking for my wages plus expenses/ disturbance.
If I’m being sent to a different country then I’d be expecting things such as flights home, reasonable accommodation, possibly even use of a car to be covered.
It can only be speculation but perhaps it was this type of demand, that the agent would be likely to be looking after, that was going to be more costly than originally envisaged/ agreed.
Loan deals, particularly where the player is having to move country are undoubtedly more complex than just covering some or all of the wages.