I am not sure that Solberg or Huttunen are the best measures for that as neither of them have any great ("normal") tarmac results from before.
But sure if they are very fast with it, it likely is fast.
Another thing is that for example Fiesta Rally2 seems to be quite good on tarmac, but not so much on other surfaces, or the current i20 has good results on smooth Italian and Spanish tarmac, but not on more bumpy rallies. Finally the Polo has a reputation of being tricky on tarmac in mixed/changing conditions but very fast in constant conditions.