Region vs Starter Movement

[the JabberwocK]

From the MELE rulebook:

6 · MOVEMENT
If region movement is being used, Ringwraith players may use METW region cards (or an appropriate, mutually
acceptable map).
Your Ringwraith company may not use region movement.

Have there been any clarifications on what "if region movement is being used" means exactly?

I had previously assumed that most players agree to use region movement before the game (using a map) and that meant that all movement which was not Under-deeps movement or Special movement throughout the game was understood to be region movement (unless specifically prohibited for Ringwraith companies).

However, it has come somewhat recently to my attention that players can strategically decide which companies will use region movement and which will use starter movement each turn, rather than all companies using region movement instead of starter movement if legally permitted to do so.

Is this the standard accepted approach to movement in most games? Particularly at tournaments, is this how the game is played? (ie. You declare at the beginning of each company's M/H phase if they will use region or starter movement that turn)

[Konrad Klar]

It is decided in organization phase for each company, whether it will move or not, and if it will move, which type of movement it will use.
It is also decided at the beginning of next M/H phase of a company if the company takes extra M/H phase.

Independently a players may decide that a region movement will not be used in game at all. In past, when a region cards was used, possessing a more number of region cards than opponents have would give (too) big advantage, so such agreement would make more of sense than in situation when a map is used.