`| and order on arrays

I thought `| should keep the order when used on arrays:

Pike v7.3 release 62 running Hilfe v3.5 (Incremental Pike Frontend)

({1,2,3}) | ({2,4,1,17});

(1) Result: ({ /* 5 elements */ 3, 2, 4, 1, 17 })

Looks like it keeps the order in the second array, but the remaining elements in the first are swapped in this case. I furthermore expected the elements in the first array to remain unchanged with precedence over those in the second, since that makes it behave more consistently when used as |=, in which case all the elements in the left operand would remain on the same indices.

Wasn't this discussed and supposedly fixed some time ago (half a year or so)?