I unlocked the Seraphic Deepsight Bonus upgrade at the Exo Frame and since then, I have gotten two Deepsight weapon drops from locked Seraph chests for weapons I've already unlocked the crafting pattern for. These weapon drops happened when I got two pieces of gear and the other gear in both instances were armor so the weapons had to be procced by this upgrade. In case it matters, the first weapon was Retrofit Escapade (the machine gun) and the second was Tripwire Canary (the bow). In both instances, I had confirmed acquiring these patterns in the Patterns and Catalyst section of the menu prior to running the heist. Based on how the description of the upgrade is phrased, this seems to be a bug because it's supposed to award a weapon I haven't unlocked the pattern for (I have not unlocked the patterns for the trace rifle and glaive). Additionally, since it says "seasonal weapons" and not "Seraph weapons," it should also include the IKELOS weapons as I haven't unlocked any of them.