Short answer. Yes, it matters — unlike personal property. Article 941 makes a devise of indeterminate real property valid only if the estate actually has immovable property of that kind, while a legacy of generic personal property remains valid even if the estate has none of that kind at all.
What the law says
A devise of indeterminate real property shall be valid only if there be immovable property of its kind in the estate.
Civil Code, Article 941 — Generic Legacies. Read the full provision →
What the law says
A legacy of generic personal property shall be valid even if there be no things of the same kind in the estate.
Civil Code, Article 941 — Generic Legacies. Read the full provision →
Generic personal property: valid regardless of what the estate holds
Article 941 treats generic personal property leniently: a legacy of generic personal property shall be valid even if there be no things of the same kind in the estate. If your father's will left you an unspecified car, or an unspecified sum of jewelry of a general type, that gift stands even if the estate turns out to own nothing of that kind at his death — the estate simply has to acquire or provide something matching the description.
Indeterminate real property is held to a stricter standard
Land is treated differently. The article requires: a devise of indeterminate real property shall be valid only if there be immovable property of its kind in the estate. An unspecified piece of land given to you by will is only a valid devise if the estate actually contains immovable property fitting that description. If the estate holds no land of the kind described, this particular devise does not stand the same way a generic personal-property legacy would.
Who picks which specific parcel or item is delivered
Once either kind of generic gift is valid, someone still has to decide exactly what is handed over. Article 941 gives that job to the estate's representative: the right of choice shall belong to the executor or administrator who shall comply with the legacy by the delivery of a thing which is neither of inferior nor of superior quality. You do not get to pick the specific parcel or item, and the executor or administrator cannot satisfy the gift with something noticeably worse — or need not give something noticeably better — than the average of what fits the description.
Why this distinction matters for your unspecified land
Because your gift is real property rather than personal property, the estate's actual holdings matter in a way they would not for a generic personal item. Before you can be confident the devise of land is valid and enforceable, it is worth confirming the estate genuinely includes immovable property of the kind your father's will describes — that condition is built into Article 941 itself, not an extra formality layered on top of it.