I just found an item in The West Briton and Cornwall Advertiser, July 1996 which announces that someone has bought the Pendarves Arms, Beacon. Then an item in the same newspaper, a summary of a local football league from December 1996, refers to a team from Beacon Inn (formerly Pendarves Arms)
Thus it seems that the name was finally changed in 1996 and that the use of the name Beacon Inn in the 1863 newspaper item was something of an anomaly.
The 1911 census has Edwin Butler, 32, innkeeper at the Pendarves Arms, Beacon. His probate indicates that he was still the innkeeper at the Pendarves Arms when he died in March 1921. I haven't tracked down an entry from 1921