Subsequent predictive distribution of BRMS (logistic regression)

Question

I am a beginner for stan, and brms, and I'm having problems with removing the posterior predictive distributions. Say I have a simple logistic regression

fit = brm(y ~ x, family="bernoulli", data=df.training)

where yis binary and xcontinuous. For test data (or even training data), I thought that now I can get a predictive distribution for the Bernoulli probability by pchanging probsto

predict(fit, df.test, probs=seq(0, 1, 0.1))

However, although the output of this command gives me estimates that are continuous in the range [0,1](this makes sense), the values ​​of the confidence interval seem binary (this does not make sense to me) ... How do I get all the subsequent predictive distribution for p?