Formate does indeed act as a reducing agent under appropriate conditions, but its byproduct is typically CO2 gas, not formaldehyde (HCOO- -> CO2 + H+ + 2e-). Aldehydes are generally unstable with respect to disproproportionation and are therefore unlikely reaction products.

Organoaluminum compounds are molecules with direct Al-C bonds, whereas these are effectively normal ionic salts with some unusual unit cell structure. Conflating DiBAl with aluminum formate is akin to conflating chlorine gas with clhoride anion...