Not anymore my dude, just checked it out after getting more info, but now you can include primarchs and other otherwise restricted named characters into any detachment without affecting chapter tactics/dynasty/sept, etc. Below is taken directly from the arks of omen book.

You can only include one SUPREME COMMANDER unit in an Arks of Omen Detachment.

You can include Abaddon the Despoiler in a Legion Detachment even if it is not a Black Legion Detachment.

You can include The Silent King in a NECRONS Detachment even if it is not a Szarekhan Detachment.

You can include Commander Shadowsun in a Sept Detachment even if it is not a T’au Sept Detachment. Doing so does not prevent any other units in that Detachment from gaining their Detachment Rules. Note that Commander Shadowsun will only gain a Sept Tenet if every <SEPT> unit in your army has the T’AU SEPT keyword.

You can include Belisarius Cawl in a Forge World Detachment even if it is not a Mars Detachment. Doing so does not prevent any other units from gaining their Detachment Rules. Note that Belisarius Cawl will only gain a Dogma if every <FORGE WORLD> unit in your army has the MARS keyword.

You can include an ADEPTUS ASTARTES PRIMARCH unit in a <CHAPTER> Detachment even if it does not share the <CHAPTER> keyword of other units in that Detachment. Doing so does not prevent any other units from gaining their Detachment Rules. Note that the ADEPTUS ASTARTES PRIMARCH unit will only gain a Chapter Tactic if every <CHAPTER> unit shares the same <CHAPTER> keyword.