Multiple rules for one target

[ali hagigat]

In the following I have two examples and their results by 3.81. In the
second example where we have two pattern rules for e13 why the rule
for ./%13 is not considered? like the first example. In the second if
I change the rule for %13 to:
%13: e14
Then the rule for ./%13 is computed. What is the logic behind this
decision. It seems different with regular rules for no reason.

--------------------------------------------------------
e12: e13
        @echo 12complete
e13: e14
        @echo 13complete_1
e13: e15
        @echo 13complete_2
e14:
        @echo 14complete
e15:
        @echo 15complete

15complete
14complete
13complete_2
12complete
--------------------------------------------------------
e12: e13
        @echo 12complete        
%13: e15
        @echo 13complete_1
./%13: e14
        @echo 13complete_2
%14:
        @echo 14complete
e15:
        @echo 15complete

15complete
13complete_1
12complete
------------------------------------------