Barry may have used the speed force to super charge the heavy water that gave Jay superspeed.
Blah! That's just... poor (Like the 1990's story which revealed the Crimson Avenger, DC's first costumed hero back in the 1930's, was actually secretly avenging the death of Superman at the hands of Doomsday, in a vision of the future the WWI soldier who became the CA had thanks to Rama Kushna, always truck me as the worst sort of hagiography.
Might it be connected to a story detailing the end of Barry's life where we discovered that as hie body disintegrated in Crisis, some sort of energy form was left that kept zipping along through spacetime and ended up becoming the lightningbolt which hit the cabinet of chemicals.