Bolton left as National security advisor in 2019. Normally he wouldn't have kept his SS protection but an exception was made due to threats from Iran. Biden in 2021 extended the protection. The feds dropped the charges against the guy that they had arrested in the plot against Bolton. Trump stopped his protection.
He has made enough money on the circuit bad mouthing Trump to afford to pay for some security if he feels that he needs it, IMHO. No reason to keep making an exception for him. Petty? I don't know..but I'll bet Trump really liked signing that order.
I know I would have.