VS Code Snippet Confusing Transformation

Question

I don't understand why this works:

"test": {
    "prefix": ".test",
    "body": [
    "${1/(.*)/${1:/downcase}/}",
    "${2/(.*)/${1:/downcase}/};"
    ]
}

as opposed to below, which doesn't work, the 2nd tabstop gets cleared after you tab:

"test": {
    "prefix": ".test",
    "body": [
    "${1/(.*)/${1:/downcase}/}",
    "${2/(.*)/${2:/downcase}/};"
    ]
}

you'd expect in the first example that it would replace the 2nd tabstop with lowercase data from the 2nd but it makes the 2nd tabstop's data lowercase