Multi-line triggers created through AddTriggerEx() don't work

Examine the following single-line trigger:

Trigger = [[^You poke (?P<thing>.+)\.$]]
Script = [[print("Poke: %<thing>")]]

AddTriggerEx("Test_Trigger", Trigger, Script,
   trigger_flag.Enabled + trigger_flag.RegularExpression + trigger_flag.Replace
   + trigger_flag.KeepEvaluating, -1, 0, "", "", 12, 0)

It works as it should. See the following test:

You poke a rock.

Output:

Poke: a rock.

Now try the same thing with a multi-line trigger:

Trigger = [[^You poke (?P<thing1>.+)\.$\n^You prod (?P<thing2>.+)\.$]]
Script = [[print("Poke: %<thing1>")
print("Prod: %<thing2>")]]

AddTriggerEx("Test_Trigger", Trigger, Script,
   trigger_flag.Enabled + trigger_flag.RegularExpression + trigger_flag.Replace
   + trigger_flag.KeepEvaluating, -1, 0, "", "", 12, 0)

SetTriggerOption("Test_Trigger", "multi_line", "y")
SetTriggerOption("Test_Trigger", "lines_to_match", "2")

With the following test:

You poke a rock.
You prod a rock.

There is no output. It does not match. However, if I open the trigger in the configuration window -do nothing- and click "OK" then it works as expected with the following output:

Poke: a rock
Prod: a rock

So for some reason these triggers aren't being evaluated when added by AddTriggerEx() and subsequently set as a multi-line trigger with SetTriggerOption().