How does twisted pair turn rate affect interference rejection bandwidth?
As I recall from doing this 40 yrs ago, twisted pair was about 240 to 120 Ohms  differential impedance depending mostly on the insulation thickness.  The closer the conductors the more capacitance and lower impedance while increasing  the number of twists per unit length increases both the capacitance and inductance so the change is less significant, where \$Z= \sqrt \frac{L}{C}\$ .
Meanwhile the crosstalk is the result of a coupled input signal.  The attenuation ratio of E field in free space to impedance of the cable and the tolerance of wire mismatch will be effectively cause poor CMRR similar to a say 1% resistor (-40dB CMRR)  unlike a -100 dB CMRR in an INA (INstrument Amp). As you go to &quot;far field&quot; this imbalance can improves.
When that cable has a differential signal it is easy to understand the induced crosstalk is greater when the load impedance is mismatched and thus \$V(F)=I(f)*ΔZ(f)\$.
Wire  Inductance per m depends slightly  on L/D ratio from 0.5uH to 1 uH /m  Wire Pair Capacitance per m length depends on gap of insulations.  Both L,C increase with twists per cm or inch.
I would expect (but never measured)   insulation thickness of 2 strands is approx equal to wire diameter to get the rated impedance of the twisted pair.
Ribbon cable I recall was 200 to 220 Ohms.
As I recall each twist adds about 1 pF but I am not sure about L.
But it is harder to visualize  say a 0.2% mismatch in coupling capacitance or inductance unless you have perfect uniformity and it the twists are far away from the interfering source.
For an E field in [V/m] the coupling is capacitive and for a B field it is inductive [A/m] while the bandwidth of the signal is limit by the 0~90% risetime \$BW_{-3dB} = 0.35 /T_r\$

If your impedances for source or load are high, adding more twists will reduce your bandwidth from dV/dt=I/C by adding more capacitance which may reduce broadband spike interference but also signal bandwidth.
If your source/load impedances are low and somewhat matched then your signal BW is increased and CM attenuation from impedance ratio is improved. Thus  adding more twists may not be as significant.

Since CAT 5 uses matched impedance applications, I suspect the number of twists is far  more tolerant than the insulation thickness to wire thickness ratio.
Beyond 1GHz you need a shielded pair for adequate SNR even with the best BALUNs.
That's my hand-waving argument for today.