Had this person's ticket all been under 1 PNR there probably would NOT have been a problem, as it was a separate nested ticket, that raised flags. Routing via OSL for no apparent reason (saving a few $ is not considered one really in this case) raises alarm bells. There is no actual requirement to start travel in the country which issued the Schengen visa, HOWEVER there are normal interpretations of that, and extraordinary ones. If one were traveling CGK-CDG via AMS, and it was one ticket (and with a French issued Schengen visa) no question would ever be asked, because it is obvious what one is doing. Also, if one had an Italian issued Schengen and was traveling to NCE, and simply said, I am driving.taking the train to Italy, or whatever, there would be no further questions. However if one has a visa issued by Italy, and starts ones first trip in a decade from Sweden, and is doing so essentially with a second ticket, on a cheap LCC, that will raise alarm bells.

But let me bring up a slightly different thing to the OP. It is incredibly likely that if they DID in fact let you do this that you would/will have issues the next time that you get a Schengen visa. The Nice/Italy example above is an actual case that I know of whereby a person that I know had no problems traveling to Nice in order to go to Italy. This is a person who had held 2 year Schengen visas concurrently since the Schengen came into being. When this person next applied for a Schengen, the Italians only issued an 8 day visa (a day longer than the trip) because this person, "Never entered Italy" with their previous visa. Despite appeals, and sending in "proof" of having actually traveled to Italy, they would not budge. Six months later when this person applied for a German Schengen Visa, she was only issued a one month visa, and it has gone this way for a couple of years now. Because as in many countries the Schengen countries have combined their visa processing, one mark, as spurious as it may be, can effect you across all countries for future visas.