How does the timing belt tensioner on Diesel P3's work?

[theobviousfaker]

Fellow gearheads,

today I have replaced the timing belt (and lots more) on my 2010 V70 D3 engine. Though I would like to check with your wisdom whether I tensioned the belt correctly.

The tensioner looks like this: https://www.fcpeuro.com/products/volvo- ... 30637955oe

The installation goes something like this:
1. The tensioner is aligned with the engine block and bolt inserted but not tightened
2. Timing belt is installed
3. To tension the timing belt, use a hex bolt to turn the excentric inner ring either clockwise or counter-clockwise (there are videos out there with both directions!). Both directions seem to work equally well in tensioning the belt.
4. Tighten the main bolt of the tensioner.

When done, the belt can still be de-tensioned by moving the spring tab clockwise. At the same time, the tensioner only statically tensions the belt, meaning there is no spring pressure on the belt. Is this how it is meant to be? No automatic tensioning of the belt?

What would be the point of the movable spring tab, then? It seems like a massive over-engineered feature, if it is only meant to assist removal/installation of the belt, as I think it can be achieved without it.

On older Volvos timing belts were automatically tensioned. I expected this here as well. It could in principle be achieved by pre-tensioning the spring tab against the alignment tab. But in that case I would have expected some plastic piece coming with the replacement tensioner.

Can someone wisen me up?