I have 4 VEGA 56 (3 ref & 1 peace of sh..)
I was at 7500-7520h/s and now I'm at 7620-7630h/s with the same "summer" profile (CC:1340Mhz / MC:900Mhz)
that doubling trick doesn't work for me, but I have 7920-7925 h/s without it on 4 vega56 (ref or noname idk, it was OEM and the only sign on it is RADEON), cc 1450-1470, mc 925-935 (found exact stable maximum for each card).
I don't know wether the trick works or not and I don't care, +20h/s? no big deal!
BTW, if you have only RADEON written on your vegas, you have ref cards

My non ref card (hynix memory) runs stable at 1775 with higher consumption

My 3 ref cards (samsung memory) go over 2000h/s with CC:1407 / MC:941 but run too hot so I lower the frequencies during the summer
Any extra hash rate you can get is a great thing. It isn't that much per card, but if you have multiple it does add up.