https://en.wikipedia.org/wiki/Tangram etc.

Don't normally use capitals for the names of games, etc.

@@ -21 +21 @@
-<gloss>dissection puzzle (Tangram, Sei Shonagon Chie-no-Ita etc.)</gloss>
+<gloss>dissection puzzle (tangram, Sei Shonagon chie-no-ita, etc.)</gloss>

OK then.

jwiki(シルエットパズル) defines 知恵の板 as
正方形などの図形を数片（5-10片くらいの範囲が一般的）に分割し、さまざまな形を作るもの。タングラムが代表的な存在である。
Then they give a list of 11 such puzzles,
including タングラム and 清少納言知恵の板

jwiki(シルエットパズル)

@@ -14,0 +15 @@
+<xref type="see" seq="2829441">シルエットパズル</xref>
@@ -19,2 +20 @@
-<gloss>Sei Shonagon's plank of wisdom</gloss>
-<gloss>Japanese puzzle similar to Tangram</gloss>
+<gloss>dissection puzzle (Tangram, Sei Shonagon Chie-no-Ita etc.)</gloss>

wiki

Compare the two images:
https://ja.wikipedia.org/wiki/清少納言知恵の板
https://en.wikipedia.org/wiki/Tangram

They're not the same. As wiki says: シルエットパズルだが分割法はタングラムと異なる

Here's the history from Wikipedia JP:

Some sort of precursor to the Tangram was invented during the Song dynasty 

Sei Shonagon's plank of wisdom appeared around 1742 in Japan.

In 1813 and in 1858, two books which form the basis of Tangram are published in China.

To me it's like saying that Kangaroos and Wallabies are the same because they're both macropods. :)

Example of someone calling it tangram-like: http://oarket.com/2014/10/15/sei-shonagon/

@@ -17 +17,2 @@
-<gloss>tangram</gloss>
+<gloss>Sei Shonagon's plank of wisdom</gloss>
+<gloss>Japanese puzzle similar to Tangram</gloss>