Obstruction or just baseball?

[mbyron]

It's hard to be sure without seeing them, but it sounds to me as if both plays are OBS under FED rules (2.22.1 C, 8.3.2 C). Blocking access to the base without the ball is OBS, regardless of whether (1) the throw moves F2 into the runner's path (8.3.2 K), or (2) the runner pulls up, thinking he's going to be tagged (the OBS gives the defense an unfair advantage here).