It was a way to get around bond regulations, the bond is a wrapper around Bitcoin. It’s similar to how some companies buy MSTR because they are not allowed to buy Bitcoin directly, but want some exposure.
A pension fund might very well be allowed to buy junk bonds since it is a well-known if risky instrument whereas bitcoin ETFs are a newfangled weird instrument that is probably not covered by their guidelines.
I mean allowed in the sense that the investment guidelines set by the board allow it.
Source: I work at a pension fund where I think we are in precisely this situation.
I think in the next few years the pressure for junk bonds like this in pension funds will just grow as inflation rate moves farther away from bond yields.
You are correct that at the time of announcement, if you had believed in Bitcoin and El Salvador (for some reason) it would have been advantageous to simply buy - separately - Salvadoran sovereign debt on the capital markets and Bitcoin on the spot markets.