The Brisk Storm Avatar was a copy of the Eternal Storm Veil Penetrator bearing half of its stats and a majority of the original abilities.
The soul it bore was a replica of what the original had, indistinguishable by means within the bounds of normalcy. However, when it came to finer details, especially for Skullius, not everything was retained.
A replica of Sila's soul couldn't be made within Replicus' body. The skill wasn't strong enough to copy two souls, especially with the fact that Sila's soul was leagues above Skullius' in quality.
Why was this relevant?
Replicus, at this moment in time couldn't use Sila to help him form multiple Ties of Exchange with these bandits. This had been something Skullius considered way back, before acquiring the [Brisk Storm Avatar]. Back then, with UNCoddled still a threat to him, he had considered that once he split, he would need new allies.