Note above the send button the number 0/3, it counted down from 160 three times, +1, converting to MMS, back to 0/3 and I'm pretty sure that says converting to SMS. People that I text get one long text not 3 separate ones.
Their text app displayed one single text message, the same as it would if it was sent as an MMS - but you can't put 40 ounces in a quart container in this universe, and you can't put more than 140 octets in a 140 octet packet in this universe.
Converting a text message to MMS means that a text file is stored on your carrier's MMS server and a link to that file is sent to your recipient. His text app downloads a single text file and displays it. The only thing sent as SMS is the link. (If the link were longer than 160 characters - which no carrier in their right mind would do - the system would send a link to the text file with that long link, which would then be used to download the text file.) It's just not possible to make 160 equal to more than 160.
Read 1.2.1 of
https://www.ietf.org/rfc/rfc5724.txt That defines what SMS is. Notice that it says "SMS messages have a maximum length of 160 characters (7-bit characters from the GSM character set [SMS-CHAR]), or 140 octets."
A defining document can't be "wrong" - it
is the definition. (You can redefine "SMS" to mean anything, but once we get into that area, communications becomes noise, not information. SMS,
as defined by the industry document that defines the term, limits SMS packets to 160 GSM characters [or 140 octets]. An app is free to combine any number of SMS messages and display the data as a single "message", but that's not making a single SMS message longer than 140 octets, any more than carrying 5 quart containers makes a quart more than 32 ounces.)