Simon Bertilsson (Flyers 2009 3rd rounder) has been skating on the same blueline since his 18/19 year old season. The Flyers opted not to sign him to an ELC. HF ranked him 14th among Flyers prospects in both Fall 2009 and Spring 2010. Undrafted Simon Lof also played 55 games for Brynas during his 18/19 year old season. Nine different players aged 22 or younger, five of which were 20 or younger, saw time on league Champion Skelleftea's blueline.
You're overrating Djoos' experience in the SEL.
I think you're underrating Djoos' experience in the SHL.
The number of games played mean absolutely nothing in the SHL. Every game that a player is listed on the roster counts as a game played, even if the player plays zero minutes. It's quite common for SHL teams to dress young players and then not play them (or play them minimally) for many games.
It's the TOI that the player is trusted to play that is important.
If you look at the Skelleftea example, their stats page shows that of the 9 young defensemen mentioned above, only 3 played more total season TOI and/or scored more points than Djoos.
http://http://estat.hockeyligan.se/c/LPlayersTimeOnIce.aspx?LId=250&GoalKeepersScope=1&TId=32&PlayerPosition=0
Each of those 3 Skelleftea defensemen was 2-3 years older than Djoos. (Burstrom, Klingberg and Alm)
Djoos averaged 15:34 per game for the season, but by the last two months was playing 18-22 minutes per game. Possibly the most important, though, was his burst of scoring that began after he returned from the WJC. On his player page, it's shown by the blue boxes that begin to appear in mid-January, as if he'd made a breakthrough.
http://http://estat.hockeyligan.se/c/LPlayer.aspx?LId=250&PlayerId=4897
This scoring didn't start as a product of his teammates' good play. It happened in spite of a nearly teamwide scoring drought from December on that nearly took Brynas out of the playoffs.
Djoos was used on the PP, PK and in OT and was even chosen for a shootout attempt.
Brynas continued to trust Djoos in the playoffs, in which he averaged 21:17, the second highest ice time on the team.
http://estat.hockeyligan.se/c/LPlayersTimeOnIce.aspx?LId=251&TId=36
As for Bertilsson and Lof. . . according to Flyers' and Brynas' sites I've read, Bertilsson wasn't signed by the Flyers because of his nearly constant injuries. Lof, because of his frequent own-zone mistakes, seems to be known among Brynas fans as the player they most want loaned to another team. Both Bertilsson and Lof are 22, and both have played 4 seasons for Brynas, but neither has scored as many points in a season or proved to be as versatile as Djoos was last season.