why would my boyfriend do this?

my bf just graduated and on his instagram, he posted his grad pics and wrote: "I am so thankful for my family, friends and my girlfriend for encouraging me and supporting me." (his grad pics showed me and his entire family)

but on facebook, he removed "my girlfriend":

"I am so thankful for my family and friends for encouraging me and supporting me." (his grad pics only show himself)

why would he do this? would you be offended if your bf did this?