If Saturn were FORTIFIED by Jupiter and Venus, then Saturn's benefic qualities would come to the fore (all other factors being equal) However, if both Venus and Jupiter were detrimented, ie turned into functional malefics, then they would in fact BESIEGE Saturn and would act to enhance Saturn's malefic qualities; the term besiege (as used by the oldtime authors) indicates malefic influences-they used the term FORTIFY for benefic containment (the word-containment-is used in Modernist astrology for placement of a planet, Lot, lunar Node or specific degree, between 2 other planets, one on each side)
If Venus and Jupiter turn into functional malefics when in detriment, then Mars and Saturn turn into functional benefics if also in detriment? I honestly don't understand why Venus and Jupiter would become malefic all of a sudden even under such conditions. Jupiter is in detriment in Mercury's domicile, but Mercury isn't a malefic planet, nor Gemini or Virgo are "evil" signs.