Ann: Vital Joins OTCQB For Trading of Shares in North America, page-8

OTC is just the "Over The Counter" trading platforms in the US. Trades will be using current shares on market.
OTC exchanges are risky for investors because they are unregulated and zero financials are required to participate.
The advantage for ASX companies is simply easier access for US penny stock investors.
I believe they can buy in very small parcels also, even one share purchases.
it's not a bad thing, but far separated from large exchanges and usually no expectations of big transactions.
maybe impactful if we can advertise in reputable Penny Stock subscription reviews etc.