the server is now able to determine
  whether block breaking is impacted by
  TPS. In vanilla, block breaking is
  determined by server TPS – if the TPS is
  lower, then block breaking takes longer.
  However, the client thinks block breaking
  proceeds at 20tps, so this can cause
  disagreements with the server on whether
  a block was broken or not. This will fix this
  by moving the server’s checks to use time
  rather than ticks as and when needed.