LTE anchor site is a site that provides the control plane for the 5G NR NSA (Non-Standalone) architecture, which means that the 5G data connection is established through the LTE layer. The LTE anchor site and the 5G NR site need to have frequency synchronization, but not necessarily phase synchronization. However, phase synchronization can improve the performance of some features, such as CoMP (Coordinated Multi-Point) and MIMO (Multiple-Input Multiple-Output).
Secondly, inter-site gNB TDD N78 layer is a layer of 5G NR base stations (gNBs) that operate in the n78 band (3.3-3.8 GHz TDD) and are connected to each other via X2 interface. This layer can provide higher data rates and capacity than the LTE layer, but it may have lower coverage and higher penetration losses.
Thirdly, DLoverF1mode is a feature that allows the gNB to deliver data to the 5G PDCP (Packet Data Convergence Protocol) layer directly, bypassing the LTE PDCP layer. This can reduce the latency and overhead of the data transmission, but it may also introduce some challenges, such as security, mobility, and QoS (Quality of Service) management.
Based on these information, my opinion is that enabling anchoring for inter-site gNB TDD N78 layer with an LTE anchor site that has no phase sync may be feasible, but it may also depend on other factors, such as the network topology, traffic demand, interference level, and user expectations. You may need to conduct some field tests and simulations to evaluate the performance and QoE of this configuration. You may also need to consider some trade-offs between the benefits and drawbacks of DLoverF1mode.