Pullback fails to inline with intervals

The following MWE does not inline when using intervals from IntervalArithmetic.jl:

function fff(x, y)
    z, z_pullback = rrule(*, x, y)
    
    z̄ = one(x)
    _, r1, r2 = z_pullback(z̄)
    
    x̄ = unthunk(r1)
    ȳ = unthunk(r2)

    return (x̄, ȳ)
end

using IntervalArithmetic

julia> @code_native f(1..1, 2..2)
	.section	__TEXT,__text,regular,pure_instructions
; ┌ @ REPL[23]:1 within `f'
	pushq	%rbx
	subq	$160, %rsp
	movq	%rdi, %rbx
; │ @ REPL[23]:2 within `f'
	movabsq	$rrule, %rax
	leaq	112(%rsp), %rdi
	callq	*%rax
	movabsq	$5516288192, %rax       ## imm = 0x148CBE0C0
; │ @ REPL[23]:5 within `f'
; │┌ @ fastmath_able.jl:188 within `times_pullback'
	vmovaps	(%rax), %xmm0
	vmovups	%xmm0, 80(%rsp)
	vmovups	128(%rsp), %xmm1
	vmovups	144(%rsp), %xmm2
	vmovups	%xmm2, 96(%rsp)
	vmovups	%xmm0, 48(%rsp)
	vmovups	%xmm1, 64(%rsp)
; │└
; │ @ REPL[23]:7 within `f'
; │┌ @ thunks.jl:99 within `unthunk'
; ││┌ @ thunks.jl:98 within `Thunk'
	movabsq	$"#461", %rax
	leaq	16(%rsp), %rdi
	leaq	80(%rsp), %rsi
	callq	*%rax
; │└└
; │ @ REPL[23]:8 within `f'
; │┌ @ thunks.jl:99 within `unthunk'
; ││┌ @ thunks.jl:98 within `Thunk'
	movabsq	$"#462", %rax
	movq	%rsp, %rdi
	leaq	48(%rsp), %rsi
	callq	*%rax
; │└└
; │ @ REPL[23]:10 within `f'
	vmovups	(%rsp), %xmm0
	vmovups	%xmm0, 32(%rsp)
	vmovups	16(%rsp), %ymm0
	vmovups	%ymm0, (%rbx)
	movq	%rbx, %rax
	addq	$160, %rsp
	popq	%rbx
	vzeroupper
	retq
	nopw	%cs:(%rax,%rax)
	nopl	(%rax)
; └

Cf. the beautiful code when using floats:

julia> @code_native f(1.0, 2.0)
	.section	__TEXT,__text,regular,pure_instructions
; ┌ @ REPL[23]:1 within `f'
	movq	%rdi, %rax
; │ @ REPL[23]:10 within `f'
	vmovsd	%xmm1, (%rdi)
	vmovsd	%xmm0, 8(%rdi)
	retq
	nopl	(%rax)
; └

Reproduce the MWE using IntervalArithmetic.jl, the fff function, rrule(*, x, y), and @code_native. Compare the interval output with the float output and trace why the pullback and unthunk calls remain uninlined. Done means the interval case produces appropriately inlined native code without regressing the float case.