To expand the question, how common is it for famous personages to view places or things that (other) people have named for them?
There is no record of William T. Sherman or U.S. Grant ever visiting the Sequoia National Park where the trees bearing their names reside. But the person who came the closest to his tree was Grant. I include the rest of the information since I spent the better part of three hours looking for an answer. General Grant's tree was named after him in 1867 so all of his California service earlier in his Army career wasn't looked at. In case you're interested, Sherman's tree was named after him in 1879.
Grant took no trips to California in the post Civil War years until 1877. I located a book titled General U.S. Grant’s Tour Around the World by L.T. Remlap. As the title says, the author documents Grant’s trip around the world after his Presidency, and from the research I’ve done, this is one of the most detailed accounts of the journey.
Grant left with his family on May 17th, 1877 and arrived eleven days later in Liverpool, England. He wouldn’t return to America for more than two years. He took this trip partly for a vacation, and also in the hope that a wave of foreign enthusiasm, for a President War Hero such as himself, might spark another run at the Presidency in 1880. While he was met with ebullient crowds on his travels through Europe, the Middle East, and the Far East this enthusiasm wouldn't carry over to another run at the Presidency when he arrived back in the United States.
Grant’s journey home terminated in San Francisco on September 20th, 1879. And after a few days in the Bay Area, on October 3rd, he took a stage coach to Yosemite Valley. Upon their arrival in the valley the Grant’s said it, “Surpassed anything they had observed on the Rhine or in Switzerland” during their world tour. Apparently Mrs. Grant was so moved by the landscape that she caused their stage driver, Monroe, to remark, “I never hauled a lady over these roads who was so enthusiastic.” After the group stopped at Lookout Point, they traveled to Inspiration Point for a view of the entire valley before the coach trundled on.
It was said, “The General allowed no object of interest to escape him. He noted all the domes, roads, and peaks, and asked Monroe about heights and distances.” They spent the next three days in Yosemite touring the major attractions like Glacier Point, Sentinel Dome, El Capitan, the Three Graces, the Three Brothers, Half Dome, North Dome, and Yosemite Rock.
Even though Grant never saw his tree in person we do know he was impressed with the Yosemite Valley scenery which is similar to the one you will find in Sequoia National Park. So if Grant had been able to see the massive tree—measuring 267.4 ft from above the base—it’s reasonable to assume he would have been proud to have it named after him.
SOURCES:
Wendell Flint (1987). To Find the Biggest Tree. Sequoia National Forest Association. p. 94.
L.T. Remlap (1880). https://archive.org/details/generalusgrantst00reml Pgs. 330, 384-386.
http://www.pbs.org/wgbh/americanexperience/features/general-article/grant-tour/