Utilizing　exact　diagonalization　techniques,　we　investigate　a　one-dimensional,　nonreciprocal,　interacting　hard-core　boson　model　under　a　Stark　potential　with　tail　curvature.　By　employing　the　nonzero　imaginary　eigenenergies　ratio,　half-chain　entanglement　entropy,　and　eigenstate　instability,　we　numerically　confirm　that　the　critical　points　of　spectral　real-complex　(RC)　transition　and　many-body　localization　(MBL)　phase　transition　are　not　identical,　and　an　examination　of　the　phase　diagrams　reveals　that　the　spectral　RC　transition　arises　before　the　MBL　phase　transition,　which　suggests　the　existence　of　a　non-MBL-driven　spectral　RC　transition.　These　findings　are　quite　unexpected,　and　they　are　entirely　different　from　observations　in　disorder-driven　interacting　non-Hermitian　systems.　This　work　provides　a　useful　reference　for　further　research　on　phase　transitions　in　disorder-free　interacting　non-Hermitian　systems.　©　2023　American　Physical　Society.