Roll bar connection

[69stang]

It looks like an engineering solution of a manufacturing decision. Because the parts have a step in them to help lock them together and wanting equal thread depth or thread engagement in each hole which translates to equal clamping force the solution is opposing fasteners (one hole threaded & one hole thru per part). Result being both halves are the same part (ease of manufacturing). That would be my educated guess. Also throw in there reduced part count - 2 machined parts & 2 bolts vs 2 machined parts, 2 bolts & 2 nuts - had they gone with 2 thru holes per part.