They may ask for some kind of proof that your income has dried up. Easy if you have your own business to show that it was non-essential and thus you had to close. Or if you were furloughed - like a neighbor whose son was working at the DMV -, you’d have a letter from your employer that you could provide the bank.
But yes, in most cases, it should not be too hard to find even a small way in which your business was financially impacted. Whether that’ll qualify for forebearance, that’s another question. IRS may give guidance to the banks but they’ll ultimately decide whether to grant it or not.
But for me, there’s also the issue of civic and ethical responsibility. Personally, I’ve been blessed to be very minimally impacted financially (and don’t anticipate any change in the next 6 months) so I’d consider it wrong to ask for being granted 90 day forebearance. To go through the paperwork just to float an extra $5k for 3 months at 1.5% APY to make $20 while others experience tremendous health and financial hardships? Plus what if my application for forebearance slows the system down and delays someone who really needs it? Doesn’t seem worth it for me but it depends on everyone’s circumstances and ethical line in the sand.