Well, when we first saw Boruto absorb the flames, yeah I was thinking that the karma might grant the ability of the Otsutsuki you kill.
However, in order for this conjecture to remain valid, we would have to find out that Jigen killed an Otsutsuki. What's more, if Kawaki's karma has the same power as Jigen's (since Jigen is the source of Kawaki's karma), then this would mean that the Otsutsuki that Jigen killed would have also had to have absorb and release powers like Momoshiki (since Kawaki has shown absorption and release with the karma).
For right now though, we don't know how Jigen got his seal.