is that the same as the time when an abort sequence was initiated?

You can watch it on SpaceX' video - the instruction 'hold hold hold" is given at T-00:00:15, the clock freezes a couple seconds later, and shortly after that, you hear "launch abort is started".

https://www.youtube.com/watch?time_continue=1834&v=V5bG37hzw...

  Is the timer freeze standard?

It's mission dependent. Some missions allow for the clock to be paused, then resumed [1]. Some missions have prearranged holds [2] built into the mission plan.

For a mission to the ISS, the launch window is too short to hold then resume, so a hold on an ISS launch is effectively a launch abort.

[1] https://en.wikipedia.org/wiki/Space_shuttle_launch_countdown

[2] https://en.wikipedia.org/wiki/Built-in_hold