IMO this rule is not being followed by many dealers due to the reason that GST Portal poses no such restriction.
BUT it should be kept in mind that as pet Rule 21(g)-Registration is liable to be cancelled if Rule 86B is not followed.

Also another important aspect is that payment under RCM is not to be considered while calculating the 1% payment from cash ledger on cumulative basis, as one of the provided exceptions.

Read the break up of R.86B⬇️
Stay tuned for case studies on the same