It's sort of ambiguous what "official" means in this context.

For example, your player wouldn't be allowed to use the older version of the enchantment in an Adventurer's League game -- but Adventurer's League is 5e now anyway, so in some sense there is no "official" any more.

As the DM, you have the authority to allow or disallow material from any sourcebook. So the question you should be asking is not: "is this official, in some hypothetical official 3.5e setting?" but rather "should I allow this in my game?".

To understand that question, we should think about why the original might have been banned. Hey I Can Chan's answer, on this post, has a good possible reason: the original version of the enchantment was very swingy, in a way which might have one-hit-killed a PC, and that's not good for the game.

In terms of game balance, we discussed it in the post linked above and found a clear answer: this weapon enchantment is not broken, and in fact it's considerably weaker than some other common enchantments your player could get. Even if your player has a specifically crit-focused build (which, presumably, they do?), this weapon enchantment is only a marginal improvement.

If your player wants to take this, it's fine to let them have it.

It's sort of ambiguous what "official" means in this context.

For example, your player wouldn't be allowed to use the older version of the enchantment in an RPGA game -- but RPGA was replaced by Adventurer's League, which is 5e, so in some sense there is no "official" any more.

As the DM, you have the authority to allow or disallow material from any sourcebook. So the question you should be asking is not: "is this official, in some hypothetical official 3.5e setting?" but rather "should I allow this in my game?".

To understand that question, we should think about why the original might have been banned. Hey I Can Chan's answer, on this post, has a good possible reason: the original version of the enchantment was very swingy, in a way which might have one-hit-killed a PC, and that's not good for the game.

In terms of game balance, we discussed it in the post linked above and found a clear answer: this weapon enchantment is not broken, and in fact it's considerably weaker than some other common enchantments your player could get. Even if your player has a specifically crit-focused build (which, presumably, they do?), this weapon enchantment is only a marginal improvement.

If your player wants to take this, it's fine to let them have it.