Murex trunculus as a chumra would be below wool tzitzis, Chalav yisroel, pas yisroel, yoshon, zman mogen avraham for krias shema, etc. Those have reliable psakim to back them up. There are serious questions on this, as Rav Shmuel miller pointed out. And how can the Jews have lost a process that their neighbors next door were still using?
Finally, the latest archaeological evidence shows a darker techeiles color than what is being use.
The dye from murex trunculus changes color depending on exposure to sun. It can have many shades.