Short answer. Yes, in a specific sense. Rule 39, Section 47(a) treats a judgment on the probate of a will as conclusive upon the will itself, binding beyond just the parties to the case, unlike judgments in ordinary civil cases. The one carve-out: probate is only prima facie evidence of the testator's death, not conclusive on that point.
What the law says
In case of a judgment or final order against a specific thing, or in respect to the probate of a will, or the administration of the estate of a deceased person, or in respect to the personal, political, or legal condition or status of a particular person or his relationship to another, the judgment or final order is conclusive upon the title to the thing, the will or administration, or the condition, status or relationship of the person
Rule 39, Section 47 — Effect of judgments or final orders. Read the full provision →
What the law says
however, the probate of a will or granting of letters of administration shall only be prima facie evidence of the death of the testator or intestate
Rule 39, Section 47 — Effect of judgments or final orders. Read the full provision →
What Section 47(a) says about probate judgments
Rule 39, Section 47(a) singles out probate of a will as a special category. It states: "In case of a judgment or final order against a specific thing, or in respect to the probate of a will, or the administration of the estate of a deceased person, or in respect to the personal, political, or legal condition or status of a particular person or his relationship to another, the judgment or final order is conclusive upon the title to the thing, the will or administration, or the condition, status or relationship of the person."
Why 'conclusive upon the will' reaches beyond the parties
The key phrase is "conclusive upon the title to the thing, the will or administration." That is different from the ordinary rule for most judgments, which binds only the parties and their successors. A judgment conclusive upon the will itself, rather than merely between two litigants, is what makes a probate decree effective against the world at large, not only against whoever happened to appear in that particular case.
The one specific exception
The same subsection carves out one limit, immediately after: "however, the probate of a will or granting of letters of administration shall only be prima facie evidence of the death of the testator or intestate." On every other point — the will's validity, its due execution, and similar matters — the probate is conclusive; on the specific fact of the testator's death, it is only prima facie, meaning it can still be contradicted by other evidence.
What this means in practice
Because probate falls under this conclusive category rather than the ordinary between-the-parties rule, a will that has been probated is treated as validly probated as against everyone, not just those who took part in the proceeding — someone who never appeared in the case cannot simply relitigate whether the will was validly probated in a separate action. The narrow exception is that the fact of death itself remains open to being shown otherwise, even after probate.