Unfortunately, it never checks the return value so it continues on with the rest of the bytes in the I2CWRITE statement (here you have four of them).
Not what i find . it may vary by pic18/16 and/or pbp version
i my test the transaction terminates at the first nak and is followed by a "funny start" dud transaction , the data in the sq brackets is never sent

Name: Screenshot 2023-03-19 152852.png Views: 506 Size: 95.6 KB



pic18f45k80
Code:
'OSCTUNE.6 = 1 ; Enable 4x PLL
OSCCON = 110000




TRISD=000110 'set PORTD 


define OSC 16
DEFINE I2C_SLOW 1
ADR VAR BYTE
ADR2 VAR BYTE
CMD  VAR BYTE
ADR=$48
ADR2=$70   


SDA VAR PORTD.3
SCL VAR PORTD.2




CMD= $48


FEDO:
I2CWRITE SDA,SCL,ADR,[5]
I2CWRITE SDA,SCL,ADR2,CMD,[3,4]
PAUSE 250
I2CWRITE SDA,SCL,ADR,[0]
I2CWRITE SDA,SCL,ADR2,$48,[2,7]
PAUSE 250
GOTO FEDO
edit
might be a proteus artifact also, i have not scoped it