Calling .tz("UTC", true) after .tz("UTC") on the same object seems to mutate it

[KevinMoran99]

Describe the bug
When creating a dayjs object and changing its timezone to any zone with 0 offset (UTC, in this example, for simplicity), then calling .tz("UTC", true) on the same object, it appears as if it has some kind of mutation.

Using isSame to compare the object with a copy of itself that was declared before calling .tz("UTC", true) returns false, although in the console both objects seem to have equal values.

Reproduction on Codesandbox

As stated, this happens with all zones with 0 offset, so, for instance, replacing 'UTC' with 'Africa/Abidjan' in the code yields the same result.

In general, everything utc related seems to be kinda weird right now, as there are some other shenanigans that I have encountered in our actual project but can't find a way to properly reproduce them in an isolated environment.

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Expected behavior
isSame should return true due to immutability.

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Information

• Day.js Version: v1.11.13
• OS: macOS Monterey 12.5
• Browser: Chrome 127
• Time zone: GMT-06:00, also happens when using the browser's console to emulate a timezone with a positive offset, such as GMT+01:00.