REST API create and update product have differ product tagging rules

[Vostario]

Create product:  

"product" => [
"title" => "Burton Custom Freestyle 151",
"body_html" => "<strong>Good snowboard!</strong>",
"vendor" => "Burton",
"product_type" => "Snowboard",
"tags" => ["Barnes & Noble", "Big Air", "John's Fav"]                        -- (array)
]

Update product:

"product" => [
"id" => 632910392,
"tags" => "Barnes & Noble, John's Fav"                                               --(string)
]