Fleece Tyler is not a legendary freestyler like it sounds. He is actually just an extremely obscure internet meme that only freestylers are likely to have encountered, while using Google Translate to translate Japanese freestyle-related web pages (such as freestyle-sk8.com) to English.
This mistranslation occurred due to Google Translate incorrectly separating the katakana 「フリー」 (furi-) from the 「スタイル」 (sutairu) in 「フリースタイル」 (furi-sutairu). Instead, it separated it into 「フリース」 (furi-su) and 「タイル」 (tairu), which phonetically resulted in Fleece Tyler, in English.
In short, Fleece Tyler is "Freestyle"!
The original mistranslation was corrected sometime in 2016, but Fleece Tyler lives on, in our hearts, and on this page.