Data centres are becoming a growing share of electricity demand, representing a new class of large, dynamic loads that challenge traditional power system operation and analysis. System operators, including in Australia, are developing technical requirements for secure integration of data centres. Fault ride-through (FRT) compliance has emerged as a key concern following incidents where data centres disconnected during voltage disturbances. Uninterruptible power supply (UPS) architecture strongly influences FRT performance, which may be centralised at the facility or decentralised at the rack level. This paper fundamentally evaluates the withstand capability of data centres equipped with centralised and decentralised UPS systems under different system strength conditions. We clarify how critical data centre loads can be shared between the grid and UPS backup following voltage disturbances, considering power distribution equipment limits. During high-voltage disturbances, data centre withstand capability is constrained by equipment voltage limits, while during low-voltage disturbances grid power is limited by equipment current ratings. The simulation results demonstrate that the post-disturbance dynamics of hyperscale data centres are strongly influenced by UPS active power recovery and converter protection, with recovery-induced voltage excursions or sustained voltage depression becoming particularly significant under weak grid conditions. These findings highlight the need to explicitly represent UPS dynamics, rack-level battery response, and converter protection in dynamic models to accurately assess data-centre voltage stability and grid impact.