This was definitely a huge deal. One that Sylas couldn't easily put into words because of the complexities of it all.
There were two things that dictated the strength of a Bloodline. The first was obviously its Grade itself. But a Golden Bloodline established at Blood Essence wouldn't be nearly as strong as a Golden Bloodline established at Bone Essence, let alone beyond that.
For a Hero Line's weakest form to be at the Soul Construct Layer meant that Sylas' starting position when he should form his Foundation was on another level compared to anyone else.
This would have a direct benefit to his F-Grade Foundation as well, and even if he didn't successfully forge a new Hero Line just yet, or complete it to the level he wanted to, it would still have an enormous impact on how powerful he was at E-Grade.
Just the synergy between his stats, the strength of his Gene Classes, and things of the like would be on another level entirely.