They claimed that before the banking crisis, after there was considerable pressure on them to disclose where the reserves are kept (many in crypto doubted if all the money even exists). At the time it didn't look good because what everyone wanted to hear was that they keep it as cash in a bank, so the commercial paper disclosure was seen as negative and risky. Ironically it turns out that this might actually be safer than what USDC did. They played by the book and wanted to prove full solvency by having every single dollar in bank custody. Which nearly cost them their neck with the SVB failure when parts of the funds got frozen and users panicked.