Would you consider it risky for a startup to use its own product?

I would consider that a risk decreaser, because the loop creates a stronger fit signal.

Even more powerful, since across a cohort the encouragement is N-way, or really N^2-way, it actually lowers risk on average the more startups act as each others’ early customers.

And co-adopters benefit from getting unusually responsive suppliers with a strong indirect stake in mutual success.

Encourage isnt a requirement. Adopt only if it makes sense.