The SEO title and excerpt might be written in different verbiage than the article. Then, the user looking up a particular word or word group might not see that word or word group in the article.
Is this considered cloaking?
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Cloaking is when you present one page to a search engine that is different than what you present to users. What you are describing is something entirely different. I will explain.
I describe in several answers here that Google does not match search terms directly to content. While it may seem that it does, the reality is that this notion derives from highlighting search terms in the search engine result page (SERP) after a lot of semantic based analysis and algorithms are applied. It is simply the last step.
Instead, what Google does is analyze the search query for intent using as much semantic analysis as possible. It then matches it to the same semantic analysis performed on web pages. Semantics are topic based. Each term is considered in context and not directly matched. For example, the term left can mean to leave or the remainder of something or an indication of a side of something. Simply matching terms would yield in false results.
Having said that, what exists within a title tag, description meta-tag, one and only h1 tag, other header tags, and content must match topically. However, the best strategy is to create a short title for your content that is about 50-55 characters and a longer version of the same title. Both titles should be as compelling as you can make them to entice someones curiosity. The short title would be your title tag and the longer title would be your h1 tag. Then take the longer title and expand upon it to no more than 170 characters and make it more compelling. This would be your description meta-tag.
As far as terms are concerned, Google will chose not to use the description meta-tag and replace it with something else often from content but never a header tag. To better control how your site is found, figure out what the 2-3 most important search terms your page is to be found by. I do not advocate using keywords, however, you do have to use search terms that apply to the topic. Keep in mind that you need to know what people are actually searching for and not what you think they are searching for. Even then, researching for keywords is like driving looking into the rear-view mirror. Not very practical. Use these 2-3 search terms in your title naturally. Add one or two more and use these in your h1 tag. Add a few more to your description meta-tag. In order for a description meta-tag to appear as a snippet for a search term, the term must be supported in the title tag, h1 tag, as well as within content. This is key.
All search terms used within a title tag, h1 tag, and description meta-tag should exist within the content. Why? Because semantics is based upon scoring and search algorithms looking for strong semantic signals. Part of this is scoring parts of your web page to see what topics and sub-topics are where on your page and how important they are. It is best that terms you use are important terms to your pages topic. In otherwords, do not wedge terms in you think are important onto your web page. It would not be supported semantically and score very low resulting in poor search performance.
Be that as it may, the best advice is to write your content naturally using the terms that apply to the topic as you would talking to a peer. Do not get cute and try and use terms unnaturally or synonyms to influence search engines. They do not need your help. Just write as you would if you were talking to someone. Semantics will figure out what is important about your work and return the results you should have. This means happier users. Just keep one eye on your tags as I have described so that their behavior benefits you and not hurts you.