There is no necessity for 52 week contracts for 2 year or 3 year deals.
Rovers have been signing players to 40 week per season / 2 years deals for some time now
As others have pointed out the top player prospects have no desire to sign long term deals and limit their bargaining power if a UK club comes in for them. This applies to almost all the recent high profile transfers - Sean Maguire, Daryl Horgan, Andy Boyle, Richie Towell & Patrick Hoban ( I dont know the contract positions with Chris Forrester or Kevin O'Connor)
Their only risk is of a major injury, as even if a UK clubs does not come in for them, they know that they are in a position to negotiate top money on a new LoI contract