SDK issues again after Mac OS 11.2.3 upgrade

As suggested, I checked if the CLT of the SDK was removed after the Subject Mac OS upgrade. So, I re-installed the CLT via the xcode-select --install command. I then saw the following on my Mac :

$ brew config

HOMEBREW_VERSION: 3.0.6

ORIGIN: https://github.com/Homebrew/brew

HEAD: 7fb3ea78a1e5efb28ad9137ecda5d3b889eb2811

Last commit: 7 hours ago

Core tap ORIGIN: https://github.com/Homebrew/homebrew-core

Core tap HEAD: cb7b575d0b478e20169887c9183565302e66732b

Core tap last commit: 32 minutes ago

Core tap branch: master

HOMEBREW_PREFIX: /usr/local

HOMEBREW_CASK_OPTS: []

HOMEBREW_DISPLAY: /private/tmp/com.apple.launchd.TOz3R3LwSc/org.xquartz:0

HOMEBREW_MAKE_JOBS: 4

Homebrew Ruby: 2.6.3 => /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/ruby

CPU: quad-core 64-bit kabylake

Clang: 12.0 build 1200

Git: 2.24.3 => /Applications/Xcode.app/Contents/Developer/usr/bin/git

Curl: 7.64.1 => /usr/bin/curl

macOS: 11.2.3-x86_64

CLT: 12.4.0.0.1.1610135815

Xcode: 12.4

XQuartz: 2.7.11 => /opt/X11

The above seems to show that all is in order. However, now when I run port upgrade outdated I get the following warnings :

Warning: The macOS 11.2 SDK does not appear to be installed. Ports may not build correctly.

Warning: You can install it as part of the Xcode Command Line Tools package by running `xcode-select --install'.

And re-running the xcode-select --install command again results in the message telling me that it's already installed.

Does anyone have any suggestions on how to fix this?