Reuters reports, citing sources familiar with the matter

The report says that ECB sees its current pandemic emergency purchase program (PEPP) as a "far more powerful" tool to deal with the current crisis, adding that they could increase the €750 billion cap on the program if needed.

According to the sources cited in the report, the argument made is that the OMT was designed to help individual countries, and not for the whole bloc.

In any case, as I mentioned here earlier, now that they've removed the 33% issuer limit on bond purchases for the PEPP, there is little need to go pursuing other options for now. This bazooka can pack a punch but it does come with legal/political complications.