TurboTax is behaving correctly.  Section 9042(b)(5) of The American Rescue Plan Act of 2021 requires the calculation of MAGI for this purpose to add back the exclusion for unemployment benefits.

Section 9042(b):

(b) Conforming Amendments.—

(1) Section 74(d)(2)(B) of the Internal Revenue Code of 1986 is amended by inserting “85(c),” before “86”.

(2) Section 86(b)(2)(A) of such Code is amended by inserting “85(c),” before “135”.

(3) Section 135(c)(4)(A) of such Code is amended by inserting “85(c),” before “137”.

(4) Section 137(b)(3)(A) of such Code is amended by inserting “85(c)” before “221”.

(5) Section 219(g)(3)(A)(ii) of such Code is amended by inserting “85(c),” before “135”.

(6) Section 221(b)(2)(C)(i) of such Code is amended by inserting “85(c)” before “911”.

(7) Section 222(b)(2)(C)(i) of such Code, as in effect before date of enactment of the Taxpayer Certainty and Disaster Tax Relief Act of 2020, is amended by inserting “85(c)” before “911”.

(8) Section 469(i)(3)(E)(ii) of such Code is amended by striking “135 and 137” and inserting “85(c), 135, and 137”