Yes, the unbond period is 20 days.
Once you have locked your ADX on Pool Tom, you won't be able to withdraw immediately. When you request that your tokens are released, (‘Request unbond’), you have to wait 20 days to withdraw them and you will not receive rewards for that 20 days period.
Please note you can also use the Rage Leave option if you don't want to wait the 20 days for unbonding (for the full amount or a portion of your stake, up to you), but you'd only receive 70% of the ADX withdraw amount using this method. The rest of the ADX will be distributed to other stakers.