Thats because the image shows the Polish built SB Lim-2A, which apperently was armed...
SBLiM-2A was indeed armed, because that "A" stood for "Artyleryjski" - "Artillery" and meant it's reconaissance/attack version, so it had two 23mm - usually not present in that number on
standard MiG-15UTIs. Also, that big bulge on the bottom of fuselage (roughly below the point where canopy ends or below the middle of the wing) is recon camera - also
typically absent from MiG-15UTI, as well as UTIMiG-15P's - which can be actually seen on DP's sources, as well as on that photograph of the Algerian UTI.