Completion Suggester - First element of input array gives suggestion well but not the later

For completion suggestion, I have input as follow:

"input": ["", "New Playstore"]

Let say for query or '' or comgoogl, above works well. But when searching for New Playstore or new, suggestion is not displayed.

If input is reversed, the later New Playstore or new works well but not the or '' or comgoogl.

"input": [ "New Playstore", ""]

Wondering what could be its reason? Thanks in advance.
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