SMS - card slot is indicated although only one SIM card is being used

/e/ version: 0.9p-20200625
Device model: Beryllium
When it started to occur: for me recently (when I stared using only one SIM slot)
Reproducible with the last /e/ version: yes
Reproducible with LineageOS: Don't know.

Summary

My phone has 2 SIM card slots.
When the phone is used with two SIM cards, the SMS app (Message) indicates next to the space where an SMS message is being composed what card slot is active (from what card slot the message is going to be sent). This makes perfectly sense when using 2 SIM cards.
BUT: When the phone is used with just a single SIM card, the SIM card, the SIM card slot is still being shown.
I can observe this behaviour on my phone (Beryllium) after having used 2 SIM-cards until last month. What I did not test so far - if the behaviour is the same when a fresh installation behaves in the same way when only one SIM-card is being used all the time.

What is the expected correct behavior?

When 2 SIM-cards are being used there should be an indication from which card the next message is going to be sent from.
BUT: When only 1 SIM card is being active, this SIM-card indication should vanish.

Relevant screenshots

Edited Jun 02, 2021 by Manoj Nair