GG5

snell is rather old-fashioned English.

@@ -23 +22,0 @@
-<gloss>snell</gloss>
@@ -26,0 +26 @@
+<gloss>snell</gloss>

Google N-gram Corpus Counts
╭─ーーーーーー─┬───────┬───────╮
│ ハリス糸　　 │    63 │  2.3% │
│ はりす糸　　 │     0 │  0.0% │
│ 釣りハリス　 │   317 │ 11.7% │
│ 釣りはりす　 │     0 │  0.0% │
│ ハリス止め　 │ 2.069 │ 76.5% │
│ はりす止め　 │     0 │  0.0% │
│ ハリスを切る │   257 │  9.5% │
│ はりすを切る │     0 │  0.0% │
╰─ーーーーーー─┴───────┴───────╯
Jawiki: 「ハリス（鉤素）」
The previously mentioned Smk note: 新聞・雑誌などでは、「ハリス」と片仮名で書く。
When looking for " 'はりす' 釣り" basically every resulting site uses katakana (not sure how good of a criterion this is, depending on how google actually searches here)


Google N-gram Corpus Counts
╭─ーーーーーー─┬───────┬───────╮
│ ハリス糸　　 │    63 │  2.3% │
│ 鉤素糸　　　 │     0 │  0.0% │
│ 釣りハリス　 │   317 │ 11.7% │
│ 釣り鉤素　　 │     0 │  0.0% │
│ ハリス止め　 │ 2.069 │ 76.5% │
│ 鉤素止め　　 │     0 │  0.0% │
│ ハリスを切る │   257 │  9.5% │
│ 鉤素を切る　 │     0 │  0.0% │
╰─ーーーーーー─┴───────┴───────╯

That's true. Thanks

Townsend Harris is a somewhat important (at least well known) person in Japanese history.
I think you need to feed the ngrams something more specific for accurate results

Google N-gram Corpus Counts
╭─ーーー─┬─────────┬───────╮
│ 鉤素　 │     299 │  0.1% │[rK]
│ 針素　 │      82 │  0.0% │Sankoku, Smk; add; [rK]
│ ハリス │ 352.665 │ 97.5% │
│ はりす │   8.692 │  2.4% │
╰─ーーー─┴─────────┴───────╯
Many of the hits ハリス are probably from the name Harris, but I'd believe that it's still more than hiragana usage. Especially since this is from 2007 where kamala harris wasn't as relevant
Smk: 新聞・雑誌などでは、「ハリス」と片仮名で書く。

@@ -5,0 +6 @@
+<ke_inf>&rK;</ke_inf>
@@ -7,3 +8,4 @@
-<r_ele>
-<reb>はりす</reb>
-</r_ele>
+<k_ele>
+<keb>針素</keb>
+<ke_inf>&rK;</ke_inf>
+</k_ele>
@@ -13,0 +16,3 @@
+<r_ele>
+<reb>はりす</reb>
+</r_ele>
@@ -15,0 +21 @@
+<field>&fish;</field>
@@ -17 +23 @@
-<gloss>snell (fishing)</gloss>
+<gloss>snell</gloss>