All 1957-58 nickels got the large star. This thread explains it... https://www.cointalk.com/threads/1958-jefferson-nickel-star.38282/
If there are no small star coins it can not be considered a variety for the year? But does it become a variety for the series? This is kinda puzzling.
They changed the design, on purpose, for those 2 years. They are supposed to have large stars. What site on "the internet" said this is valuable?
No. All of the 57-58 are supposed to have a large star. I suppose if they were in MS condition they might considering the lower mintages for those 2 years, but the more modern Jeffersons is a soft market. I don't think the large star adds any value.
Best way to recognize the large star is by comparing the 57 or 58 with any other year. For example: This feature is unique to these dates but does nothing to impart value on the coins.