Let me try and break it down
The USMC has 2 SOF/SOC units - Force Recon and Radio Recon. For the longest time the marine corp with their "superiority complex" refused to join SOCOM saying they are better. GWOT made them miss a bunch of the budget of SOCOM so now they have created a new unit MARSOC Raiders and that unit is now part of SOCOM. Raiders was raised from Force/Radio Recon Marines.
From Wiki
"The Marine Forces Special Operations Command (MARSOC) Raider Battalions were originally composed of Marine Special Operations Teams formed from Force Recon platoons (Det One) in 2006. MARSOC now has its own separate training pipeline. Force Recon companies continue to operate and focus primarily on direct action, intelligence gathering and maritime raid operations in the visit, board, search, and seizure (VBSS) role. "
THAT BEING SAID. We actually don't know which unit it is in the Instagram Post the post only says RECON 15 MEF.
Marines have 2 units with the Acronym Recon" - Force Recon and Marine Recon. We dont know what they are refering to.