Semillion & Viog - yes
Marsanne, Grenache blanc - no, not really, but partial oak treatment helps.
However the best Condrieu perched on the Hermitage cliff edge should be drunk within 4 years.....This is the new thinking, since the beauty of the peach & orange blossom and gentian white flowers dissipates, and turns away, shy.
Keeping could take out some perceptable heat (still there though), is the 50% low alcohol Sem up to it ?

I'd be asking the same question as Shez. May be the Sem was picked before it was ripe, and therefore not enough sugar in the fermentation to produce a typical 13%, Then matured in separate vessels and blended in the final cuvee' ?
Mystery and speculation .... since the Gren B. and Marsanne would have been sugared and dosed up yeasted to 16% ! Odd, do the maths based on Rustenberg's proportions.
See what happens is best. Enjoy your week-end