Just noticed a bit of an inconsistency https://github.com/Shopify/Timber/blob/master/snippets/social-meta-tags.liquid

Line 46:

<meta property="og:description" content="{{ page_description | escape }}”>

Line 71:

<meta name="twitter:description" content="{{ product.description | strip_html | truncatewords: 140, '' | escape }}”>

Line 77:

<meta name="twitter:description" content="{{ article.excerpt_or_content | strip_html | truncatewords: 140, '' | escape }}”>

The code on line 46 is a bit more versatile. I think line 71, & 77 would be better written as:

<meta name="twitter:description" content="{{ page_description | escape }}”>

The page description is used for the meta description and automatically inherits from the product.description and article.excerpt_or_content. Using the page description gives the user that extra step of control. Sometimes the product descriptions will have html that needs to be rephrased to make sense in plain text.