He was fully vested at 20 years as a LEO. At 21 years, he can only lose pension if convicted of a limited # of actual crimes. They were threatening his pension, not removing it. As best I know as a recent fed retiree, re losing credit for a month in his retirement calculations. They may be able to delay his receiving benefits for a bit (depends on his age which I do not know,)
ETA: If McCabe was waiting to his 50th birthday on Sunday, the early firing stops him collecting until he is 62, I think. So loss of 12 years of payouts is quite significant. (LEOs get a very good deal on pension. In comparison, I had to wait until 56 and 30 years, but I wasn’t putting my live, theoretically, on the line.)