ISIS has been significantly degraded in the Philippines in recent years, but there are still substantial networks and cells of ISIS-affiliated groups active in Mindanao that maintain relative freedom of movement in core areas near Cotabato city.
So far this year, 75 militants with the Bangsamoro Islamic Freedom Fighters (BIFF), an ISIS affiliate in the Philippines, have been arrested by the security forces, highlighting the continued proliferation of ISIS-linked cells across Mindanao.
Maute Group also maintains an operational footprint across certain rural areas.
The latest US Country Report on Terrorism states that "The Philippines remained a destination for [Foreign Terrorist Fighters] from Indonesia, Malaysia, the Middle East, and Europe."
It is highly plausible that these cells would have the capacity and the space to provide training to individuals with potentially long ties to extremists in the area.
Security sources telling the ABC these details would not be speculating or basing these reports on nothing. They would have highly suggestive evidence of training that may not have been shared yet with Philippines authorities. To dismiss these claims is undoubtedly a mistake.