The era commonly known as the period of the Shoftim, Judges of the Jewish nation, spanned from the leadership of Osniel Ben K'naz through Shimshon Hagibor.
Prior to these judges, The Seder olam also notes that Yehoshuah Bin Nun also served as a Shofet for 28 years.
At the end of this period, Shmuel Hanavi, and later his 2 sons Yoel and Aviyah also served as Shoftim.
This ended the Shoftim era, and the era of Melachim, kings, began with the appointment of Shaul as the first king.
Question: Among these leaders who led the Bnai Yisrael between Osniel Ben K'naz through Shmuel and his sons all are titled in the psukim as Judges, except for 3 of them:
1- Ehud Ben Gera - See Shoftim 3:15 " וַיָּקֶם ה' לָהֶם מוֹשִׁיעַ, אֶת אֵהוּד בֶּן גֵּרָא בֶּן הַיְמִינִי, ". Ehud was called a "Helper" or "savior" rather than a Shofet.
2- Gidon ben Yoash - See Shoftim 6:14 "וַיִּפֶן אֵלָיו ה', וַיֹּאמֶר 'לֵךְ בְּכֹחֲךָ זֶה וְהוֹשַׁעְתָּ אֶת יִשְׂרָאֵל מִכַּף מִדְיָן, הֲלֹא שְׁלַחְתִּיךָ" - Gedon was also appointed as a "helper" / "savior"rather than as a Shofet.
3- Shamgar ben Anas - "וְאַחֲרָיו הָיָה שַׁמְגַּר בֶּן-עֲנָת, וַיַּךְ אֶת-פְּלִשְׁתִּים שֵׁשׁ-מֵאוֹת אִישׁ בְּמַלְמַד הַבָּקָר; וַיּוֹשַׁע גַּם-הוּא אֶת-יִשְׂרָאֵל" - a "Helper" or "savior" of Yisarel rather than a Shofet.
Why the difference between these 3 and the rest?