Do include files which contain search keywords, such as the line
"<!--#include file="includes/metaKeywords.inc" -->", used in an shtml
page get indexed accurately by the google search engine?

Yes, they will be accurately indexed.

With a server side include such as you describe and also similar
technologies like PHP, CFML and ASP all create a complete HTML
document within the server before it is delivered to the client.

From the perspective of a web browser or search bot, the parsed page
is simple HTML - the included file is just in there as text, just as
if you had copied and pasted it into the HTML file.

This is not the case however with client-side operations such as a
JavaScript include.

Also, in the case of dynamic pages, their indexing can be disrupted by
query strings and dynamic generation. While many search engines are
quite smart about dynamic pages now, some can still slip by without
being indexed. This is especially the case when you have a single file
that displays all the content (index.shtml?story=blah for example).

I hope this answers your question.
Regards,
sycophant-ga

Good in depth answer. Thanks

"Server Side includes" are just that, they get included before you or
any searchbot gets to see them. To Google is makes no difference
whether you use include or have it all in the original HTML file. The
only advantage is that is makes your code a bit tidier for you. It is
not possible to trick a search engine with includes.