There is no such thing as 'obstruction' nowadays.
Direct free kick for: push/trip/tackle/challenge and attempts (if deemed careless). If there is contact, it's a direct freekick.
Indirect freekick: the most appropriate par seems to be "impedes the progress of an opponent without any contact being made" which wouldn't apply.
To my mind, the argument raised in the studio (as I heard it) that "he didn't move his feet and therefore it's a penalty" is the wrong way round. If he had moved his feet (I don't think he did, but he did turn a shoulder which may have been viewed as self-defence), then it would have been a challenge for certain; as it was, he was run into, but they're given all the time outside the area, usually with yellow cards in tow.
The next part to the indirect freekick line above says:
Impeding the progress of an opponent without contact
Impeding the progress of an opponent means moving into the opponent’s path to obstruct, block, slow down or force a change of direction when the ball is not within playing distance of either player.
All players have a right to their position on the field of play; being in the way of an opponent is not the same as moving into the way of an opponent.
To my mind, the last line is why it wasn't given. Move his feet, and the first part doesn't apply due to there being contact (and thus it's a direct freekick).
As for Darke, no, he was practically begging for Basel to score, and regularly appears overly negative about a minor error.