I think it would be relevant to warn users when the default software stack changes, maybe as a prompt in the config menu.
The situation gets extremely confusing when not all the swan machines have the same default or with the NXCALS stack using a different python & software stack.
More than one of my colleagues faced this, and were quite puzzled as scripts suddenly stopped working. I think the ease of access is a major strength of the service, but this mix of python version and silent change of the default a huge issue.
The NXCALS stack is updated in agreement with the NXCALS developers, who validate releases. This is not done for every LCG release (as requested from them, because they want the releases to last longer than the normal ones do). For example, the “NXCALS” stack jumped directly from being based off LCG95 to LCG100.
All the changes in default stacks are announced one week in advance through the IT SSB.
If you want to write scripts to configure the environment, you need to keep up to date with the IT SSB or to write those script in such a way that they are independent from the exact Python version, e.g. reading it from the environment.