I am a new user so if you find any error in my answer kindly correct it.
Perhaps, but indirectly
Heavier elements are made in nuclear furnaces, where processs such as nucleosynthesis/neutron capture processes i.e slow and fast
In primordial black holes (a type of micro blackhole), there are no physical processes that take place inside the blackhole which will form heavier elements.
In the early universe where everything was a soup of plasma, the extreme heat and the comparatively tiny universe, acted like a star, so early primordial nucleosynthesis happened creating hydrogen and helium (and a few traces of heavier element e.g lithium), and once the universe cooled down, no more primordial nucleosynthesis happened and therefore the values of abundances of elements stayed fixed, until the first generation of stars/population III (low mettalicty stars) were born.
The first point made that even the primordial blackhole's ate the primordial plasma, Virtual particles and CMB is spot on
The second point, that it will fling it is also correct but the flinging which I think is about Hawking radiation, which is that absorbing pair of virtual particles will cause one of the particle to have negative energy while the other one escapes, and the negative energy destructs the singularity (if there is one, because quantum gravity, ruling the early universe doesn't prefers singularities).
and Hawking radiation would tear the matter into pieces that is subatomic particles like protons and neutrons and expel it (causing loss of information. Refer to the Information paradox), but the main point is that the energy of the hawking radiation in case of the smallest primordial blackholes called planck relics (Blackholes with the swarzchild radius equal to the planck length) is 3.562×10^48 watts thereby converting 100% of the mass to energy which is an huge amount of power and has the potential to heat it's surroundings (unless it is in thermal equilibrium) and thus causing nucleosynthesis (also the nucleons expelled may have collided with other atoms causing heavier elements to form) so it has the potential to create heavier metals outside the blackholes (outside the event horizon) due to the energy supplied by hawking radiation rather than inside the blackhole though the matter fallen in may or may not .
So the hypothesis is not entirely wrong but the point that the blackhole is the nuclear furnace is wrong instead the expulsion may have caused the nucleosynthesis rather than the blackhole itself so heavier elements may have formed indirectly (plus it would not have increase the mettalicity drastically).
Or else if by flinging you mean by shooting matter out of the accretion disk, the chances are rather high because if the rare accretion disk on PBH is formed by devouring population III/first gen stars (which were formed early), it may have caused nucleosynthesis because the accretion disks are insanely hot, and if the trajectory, is finetuned then the metal rich elements could have escaped from the blackholes
Also PBHs on the heavier side may have infested neutron stars and have created heavy metals
