Unexpected revalidateIfStale = false initial load behavior on key change

[sheern]

Bug report

Description / Observed Behavior

In my usage of the useSWRImmutable hook, my component has a dynamic key as state. Upon an update to this key, I expected an immediate isLoading == true (assuming that the key is brand new) as there's no cached data associated with it. Instead, there's a split second where isLoading is false before loading as normal. I've narrowed this down to the revalidateIfStale option.

Expected Behavior

When revalidateIfStale is false, the first time a key is encountered should immediately set isLoading to true as there's no stale data.

Repro Steps / Code Example

Here's a CodeSandbox of the issue. You can see the unexpected state logged in the console.

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