This is by design, `Debug.Log(...)` with any object that is `IFormattable` will automatic be displayed using an `InvariantCulture` while string interpolation will by default use the current culture.
The workaround is to explicit specify the culture you want or use `FormattableString.Invariant()` for your string interpolations to get them to display them in the same way as `Debug.Log()`
For example `Debug.Log(FormattableString.Invariant($"{DateTime.Now}"));`