HelpMeFind has just two choices:
1. armed with thorns / prickles
2. thornless (or almost)
(for which I am a little pleased actually, as I have rose bushes here which on occasions can have four prickly canes, and one utterly smooth cane.)

The source link (David Austin website) says of 'Carolyn Knight': apart from colour, all other characteristics are the same as 'Summer Song' from which it sported.

The U.S. patent for 'Summer Song' says:
Prickles: Quantity.--On main canes from base: Ordinary, 4 per 10 cm stem length. On laterals from main canes: Ordinary, 5 per 10 cm per stem length. Form.--Concave curved inward. Length.--9 mm. Color when young.--Greyed-Purple Group 185A with Yellow-Green Group 146D at tip. Color when mature.--Greyed-Orange Group 164A at base, Greyed-Purple Group 184B at tip and along upper edge. Small prickles: Quantity.--On main stalks: None. On laterals: None.

If you can work out from that what we should list, we would be delighted to correct things.
You might like to see some homework I did to teach me about prickles years ago:

PRICKLES (prickles, bristles and glands)
Thorns spring from the wood. Stiff and immovable. A Bougainvillea has thorns
Prickles grow from the bark and can be easily rubbed off. Roses have prickles. Stiff and immovable.
Bristles can be moved as the hairs in a brush

Prickle Colour Immature _______ Mature _______ Old ________
____________ red, brown, grey, white, black

Prickle Duration
Caducous when they fall with or after the leaves and don’t stay on the wood long than 2 years.
Persistent when they become entirely woody, very hard and stay several years on the old wood.

Prickles - Where and number
Thornless; Almost thornless; Few thorns; Prickly;
Sparse (placed without order here and there); Grouped (several close together at certain places, while lacking in other place); Close-set; Dispersed; Scattered; Bristles (gallica); Intermingled with bristles (centifolia); Single; In pairs; Geminate (placed in pairs); Often paired; Infrastipular or stipulary (just below the base of a leaf or stipule)

Prickle - Shape
Simple; Compound (as in R. simplicifolia (Hulthemia persica); Alike - (all straight or all hooked);
Dissimilar (some straight, others hooked); Sharp spines; Thin sharp; Needle-shaped; Curved; Large curved (tea, bourbon); Slightly curved; In an Arc; Hooked; Very hooked; Falcate (hooked like a sickle); Straight; Nearly straight (alba) ; Flattened; Thin; Slender; Thick; Wide; Broad at base; Narrow at base; Width variable; Dilated at the base; Base enlarged; Base thick; Base compressed; Base decurrent (prolonged stemwards); Winged thorns; Wing-shaped; Thorny; Strong; Fierce; Weak (easily pushed off - gallica); Short; Long; Equal; Unequal;
Prickle - Size____________

Bristles
Colour ______________;
Bristles can be moved as the hairs in a brush. Bristles; Rare; Sparse; Grouped; Numerous; Innumerable; Close-set; Stiff; Soft; Equal; Unequal; glandulose (topped by a gland; Stiff glandular hairs; Aciculi (needles); Setiform - thorns degenerated into bristles.

Glands
Colour ______; Sessile (no stalk); Pedicellate (stalk) ; Spherical; Oval; Disformed (irregular form);
Fragrant; Scentless; viscous.

I've been growing the two of them next to each other for two or three years (R. pimpinellifolia 'Rubra' is older) and so far I have noticed no difference at all. Nor in blooms neither in prickles or leaves or growth habit. I don't know if the two roses are the same but at least the two clones that i have are identical.

I don't know where they got the flower diameter of 2 inches but my flowers' diameters are about 4 to 5 inches.