`prob` argument to monitor doesn't influence output

Summary:

Monitor seems to output values for Q5/Q50/Q95 regardless of what is supplied as the value for the prob argument.

Reproducible Steps:

From the monitor examples section:

csvfiles <- dir(system.file('misc', package = 'rstan'),
				pattern = 'rstan_doc_ex_[0-9].csv', full.names = TRUE)
fit <- read_stan_csv(csvfiles)
monitor(fit)
monitor(fit, probs = c(0.025, 0.25, 0.5, 0.75, 0.975))

Current Output:

Inference for the input samples (4 chains: each with iter = 200; warmup = 100):

          Q5   Q50   Q95  Mean  SD  Rhat Bulk_ESS Tail_ESS
mu      -0.3   0.1   0.4   0.1 0.2  1.01      348      229
sigma    0.9   1.1   1.5   1.2 0.2  1.01      227      178
z[1,1]  -1.6   0.0   1.4   0.0 0.9  1.01      308      301
z[2,1]  -1.4   0.1   1.7   0.1 1.0  1.01      329      246
z[3,1]  -1.9  -0.1   1.7  -0.1 1.1  1.00      455      294
z[1,2]  -1.7   0.0   1.5   0.0 1.0  1.01      278      138
z[2,2]  -1.5   0.1   1.5   0.0 0.9  1.01      438      251
z[3,2]  -1.6   0.1   1.9   0.1 1.0  1.02      344      124
alpha    0.0   0.4   1.6   0.5 0.5  1.01      354      116
lp__   -21.5 -17.2 -14.6 -17.5 2.3  1.03      117      208

For each parameter, Bulk_ESS and Tail_ESS are crude measures of 
effective sample size for bulk and tail quantities respectively (an ESS > 100 
per chain is considered good), and Rhat is the potential scale reduction 
factor on rank normalized split chains (at convergence, Rhat <= 1.05).

Expected Output:

Columns for the quantiles specified by the probs argument

RStan Version:

2.19.3

R Version:

3.6.1

Operating System:

Ubuntu 19.10

Start with the monitor examples and reproduce the issue using monitor(fit) and monitor(fit, probs = c(0.025, 0.25, 0.5, 0.75, 0.975)). Trace how the probs argument is handled and verify that the output columns match the supplied quantiles rather than fixed Q5, Q50, and Q95 columns.