They are simulated since A/C/E was replaced by ECBOT.
For simulated stops there is a default setting: "regular trading hours" (AFAIK defined as 9:30 am to 4 pm ET on "regular trading days"). If you want to avoid trouble with "regular" trading hours" then you will have to change your TWS settings.
See TWS Configure / Order / Stop Trigger Method / Time Restriction
BTW, last Friday was MLK day (not a "regular trading day") and simulated
stops were already inactive before 4 pm ET (with the default setting).