order of relations in replicated join gets switched in a query where first relation has two mergeable foreach statements

cat replj.pig
l1 = load 'x' as (a);
l2 = load 'y' as (b);
l3 = load 'z' as (a1,b1,c1,d1);
f1 = foreach l3 generate a1 as a, b1 as b, c1 as c, d1 as d;
f2 = foreach f1 generate a,b,c; 
j1 = join f2 by a, l1 by a using 'replicated';
j2 = join j1 by b, l2 by b using 'replicated';
explain j2;


Note that in the MR plan printed below, the Load in the MR job with join operations has 'x' as the input instead of 'z' .

#--------------------------------------------------
# Map Reduce Plan                                  
#--------------------------------------------------
MapReduce node scope-30
Map Plan
Store(file:/tmp/temp101387354/tmp-125684214:org.apache.pig.impl.io.InterStorage) - scope-31
|
|---l2: Load(file:///Users/tejas/pig-0.8/branch-0.8/y:org.apache.pig.builtin.PigStorage) - scope-17--------
Global sort: false
----------------

MapReduce node scope-27
Map Plan
j2: Store(fakefile:org.apache.pig.builtin.PigStorage) - scope-26
|
|---j2: FRJoin[tuple] - scope-20
    |   |
    |   Project[bytearray][1] - scope-18
    |   |
    |   Project[bytearray][0] - scope-19
    |
    |---j1: FRJoin[tuple] - scope-11
        |   |
        |   Project[bytearray][0] - scope-9
        |   |
        |   Project[bytearray][0] - scope-10
        |
        |---l1: Load(file:///Users/tejas/pig-0.8/branch-0.8/x:org.apache.pig.builtin.PigStorage) - scope-0--------
Global sort: false
----------------

MapReduce node scope-28
Map Plan
Store(file:/tmp/temp101387354/tmp-890864787:org.apache.pig.impl.io.InterStorage) - scope-29
|
|---f2: New For Each(false,false,false)[bag] - scope-8
    |   |
    |   Project[bytearray][0] - scope-2
    |   |
    |   Project[bytearray][1] - scope-4
    |   |
    |   Project[bytearray][2] - scope-6
    |
    |---l3: Load(file:///Users/tejas/pig-0.8/branch-0.8/z:org.apache.pig.builtin.PigStorage) - scope-1--------
Global sort: false
----------------