It works as both a stabiliser and a primer in the traditional sense of the words.

Firstly, it stabilises the timber  (i.e. it makes a sound base where all the grooves and knots etc. make the surface jagged and uneven, leaving a solid coating.

Secondly, it primes the surface in preparation for the adequate adhesion of the Wood Repair Resin (very much like a specialist paint primer does prior to the first coat of paint going onto a wall etc.) 

Obviously there's no 100% correct answer to this question due to the variables of porosity etc. that exist when 'stabilising and priming' an area prior to repairing with Wood Repair Resin or Wood Repair 2-in1 Resin. The basic rule of thumb that we find works well for the majority of contractors is:

1 x set of Wood Repair Primer for every 6 x sets of Wood Repair Resin.

1 x set of Wood Repair Primer for every 20 x sets of Wood Repair 2-in1 Resin.

In short no. As with all things wood related, it's normally water ingress that's the root of all problems leading to mould, decay and rot so the dryer the timber is, the better it is to make good. When making repairs it's just as important to ensure that your substrates are as dry as possible to allow for a good bite or bond from the resin to the surface of the void. Often, a meter is used to determine the level of moisture in the timber with a minimum amount being advised as preferable to begin work. The Wood Repair Primer will stabilise slightly flaky or uneven surfaces prior to the application of the Wood Repair Resin but will struggle to penetrate into damp substrates.