Third party able to read sms or escrow messages

Who? The carriers, anybody that the carrier has authorized access, or anybody that has compromised the carrier or its personnel, or potentially captured the messages over the air if the cellular connection can be downgraded to an older and known-weak GSM connection. Probably other means are available, too.

Among other articles:

• https://krebsonsecurity.com/2021/03/can-we-stop-pretending-sms-is-secure-now/
• https://www.theregister.com/2017/05/03/hackers_fire_up_ss7_flaw/

“able” and “allowed” are two different things. I can’t think of anyone who would be “allowed” to read them, except maybe the carriers (if necessary to debug the network) or law enforcement (with a court order).

But since the messages are unencrypted, if a bad guy found a way to get to them, he or she could then read them (would be “able” to read them).