Confusing language around Swift 6 Concurrency in Package manifest

Using Swift
1

So I've been researching about Swift 6 and concurrency support.

3 pieces of documentation I found seems confusing when put together:

1. Suggestion to add StrictConcurrency explicitly

When using Swift 6.0 tools or later, use SwiftSetting.enableUpcomingFeature in the Swift settings for the given target:

.target(
  name: "MyTarget",
  swiftSettings: [
    .enableUpcomingFeature("StrictConcurrency")
  ]
)

From swift.org: https://www.swift.org/documentation/concurrency/#in-a-swiftpm-package-manifest

2. Indication that swift-tools-version 6.0 enables Swift 6 language mode

Package manifest

A Package.swift file that uses swift-tools-version of 6.0 will enable the Swift 6 language mode for all targets

From swift.org: https://www.swift.org/migration/documentation/swift-6-concurrency-migration-guide/swift6mode/#Package-manifest

3. Explanation that Swift 6 language mode guarantees StrictConcurrency

With the Swift 6 language mode, the compiler can now guarantee that concurrent programs are free of data races. When enabled, compiler safety checks that were previously optional become required.

From swift.org: https://www.swift.org/migration/documentation/migrationguide/

Conclusion and confusion

My conclusion is that adding `` will enable "Swift 6 language mode" for all targets, which in turn enables StrictConcurrency by default...

If that is the case, why would we ever manually pass the StrictConcurrency flag like so:

swiftSettings: [
  .enableUpcomingFeature("StrictConcurrency")
]

to a target when using swift-tools-version: 6.0...? :thinking:

Isn't this the default?