The Talmudic Tests for Tekhelet

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See http://tekhelet.com/pdf/hellmann.pdf where the claim was made

Even if today, with the advanced dyeing methods of indigo dyeing, there may be little difference between the strength of the two dyes, in the times of Chazal plant indigo would fade and Murex dye would not.

The article claims that when running the first test that the Talmud suggests in Menachot 42b to differentiate between Kala Ilan which is plant indigo (derived from one of two plants: Isatis tinctoria or Indigofera tinctoria), wool dyed with the ancient methods for producing Kala Ilan failed the test while the type of Techelet extracted from the (Murex) Trunculus mollusc, (advocated by Rabbi Dov Lior, Rabbi Yisrael Ariel, and Rabbi Herschel Schachter) passed.
In the last page of the article, a picture of samples that faced the test are shown.
The one major point that still has to be checked, can we say that the thread that was used to represent Kala Ilan dyed wool of Talmudic Times was really representative of the standard Kala Ilan of that time.
The author also has to answer the question, why wasn't the Talmud worried about someone inventing a new way of dyeing wool fabrics by idigo that would be more durable than the plant dye of the Talmud.