What’s the source of that data? Without dose and duration it doesn’t tell us anything, and it doesn’t explain away the mechanistic action of glucagon making the liver dump glucose into blood, The same glucagon process that clears liver fat more quickly by oxidizing that fat as it produces sugar, makes it worse at insulin sensitivity which is fundamentally a function of insulin exposure time. Carrying the extra blood sugar around that Reta causes via glucagon means more insulin exposure, making Rets inferior to Tirz at maintaining lower fasting glucose and insulin sensitivity.
Said another way:
Reta causes constant glucagon signal → liver releases glucose → blood glucose rises → pancreas secretes more insulin to compensate = higher insulin exposure.
Tirz, by contrast, lowers glucose via GLP-1 and GIP effects without raising glucagon, so less compensatory insulin is needed = lower insulin exposure.