No, when it comes to murder
U. S. Sentencing Commission’s 1990 Annual Report Table K describes average sentences in months as:
The report varies between criminal history category, but nothing comes close to the lower end of the claim.
But it might be complicated
There are factors making simple average calculation hard. 1) Commitment to mental hospital 2) Life sentence and 3) Acquittal. 4) Plea-bargaining. How many years of sentence would one assign to these when calculating average length of sentence?
Bulletin of the AAPL Vol. 10, No.4, 1982 writes
The court's disposition was also disparate between men and women.
Thirty-six percent of the female defendants were released as not guilty, or
not guilty by reason of insanity, while no male defendants were released for
these reasons. Of the males 8.7 percent (but none of the females) were
committed to a mental hospital by the courts. Even in sentencing these
defendants found guilty, the courts meted lighter punishment for the women. Some 27.3 percent of them received probation or a short (less than five
years) sentence. while only 13 percent of the men received similar sentences. On the other hand. 69.6 percent of the male defendants received a
sentence of five years to life. but only 27.3 percent of the female defendants
received such a sentence. These figures suggest the courts treat women
more leniently than they treat men in cases of spouse murder.
Granted, the study is from single state and is limited in scope.
Bonus: Glaeser et al. NATIONAL BUREAU OF ECONOMIC RESEARCH April 2000 claims in table 1: mean Prison Sentences By BJS Circumstance of Murder in case of Lover/spouse quarrel: 18.0 years. (With life sentence calculated as 50 years)
United States Sentencing Commission Quarterly Data Report reports median sentences in months as
This does not separate between males and females. Yet for murder the 2-6 years claim did not apply in 2020.