Not an expert or part of the industry, so this is a guess.
1. They may be holding those bonds to achieve a target
duration for the fund.
2. They bought the bonds at a discount, and are hoping to sell them for a profit prior to maturity.
(Those two are not mutually exclusive.)
I'm pretty certain, however, that the fund managers didn't fork over full par value for those bonds, simply for the 0.01% interest income.