[Flifuss]

to review foreign investments in the country that could affect national security

I think the operative word here is "could". The review was initiated because a foreign government has involvement in the company.

[inquest]

The impression I get is that the "could" part refers to the nature of the sale itself, not the parties to it. In other words, any takeover of port operations "could" have national security implications, according to the law, and then it falls to the executive branch to look into the matter to see if it actually does. Based on how the article you posted describes the situation, the additional 45-day period was part of the 1975 law from the beginning, but only optional. The 1993 amendment made it mandatory in those cases. There doesn't seem to be any point in enacting that amendment, unless it was mandatory regardless of whether or not the sale passed the first stage of review.