Ack. I can def shed some light on this as I just recently went through this and have another one in the hopper for an Appeal.
Although I am a bit confused by what you are saying when you say "VAC will not need to adjudicate the %". I will just go by what my process was and it was the same for my coworker too and yes VAC does need to adjudicate the percentage.
My VRAB Appeal was a Favourable Decision with a 10% percentage awarded. From there it automatically goes to VAC for adjudication on the Percentage Rating. That took a month. Once VAC was completed the adjudication on the %, I noticed a new PSC Monthly Amount in My VAC Account under Current Benefits with a VAC Decision Letter with attached Election for Lump Sum Option form. I submitted the form immediately that same day and I had my Lump Sum direct deposited in a week.
So from the time VRAB Decision to VAC Adjudication/Processing/Lump Sum deposit took 37 calendar days.