Any and all funerals, even those with Military honors can be modified to the discression of the family. I was the SNCOIC of the rifle detail for 8 months of funeral duty some years ago. We never "struck" the casket and there is no protocol in the Marine Corps funeral regulations that state such. The only thing I could think of is that maybe it was for conflicts he may have served in? Not sure, but we never did that. On a side note I read you were presented 7 shell casings. When I was on the detail we used to shine the brass before hand and after I gave the firing commands I would ceremonialy retrieve the brass, put the spent shell casings into a red velvet bag that would be inserted into the folded flag prior to it being presented. We also ALWAYS had a live bugler for taps.
On a side note, it was one of the most honorable and proud moments I've had in my 21 plus years as a Marine being on that detail. While it was VERY emotional at times it was something I will always be proud of doing. I'll never forget the family of an Iwo Jima survivor (Purple Heart, and Silver Star recipient) I buried in Wilmington NC. Gave me chills hearing the testimony of his services.