Shelflife

Referees in Ireland
In the Northampton Bath game, Bath used ten replacements.
One of those was for an injured prop but the one I'm interested in was the Barbeary one.
Up to the 58th min Bath had used 5 subs they then Replaced no 8 with no 23 (substitution no 6) leaving a replacement hooker and SH on the bench.
No 23 received a head injury and left for a HIA on 60 mins, replaced by no 8 (temp replacement).
On 71 mins 16 replaced 2 (substitution no 7)
On 72 mins 23 failed his HIA so that substitution became permanent (substitution no 8)
On 76 mins 21 replaced 9 (substitution no 9)
Is it the case that a permanent replacement of a failed HIA doesn't count as a substitution ? Or did Bath make a mistake ?
One of those was for an injured prop but the one I'm interested in was the Barbeary one.
Up to the 58th min Bath had used 5 subs they then Replaced no 8 with no 23 (substitution no 6) leaving a replacement hooker and SH on the bench.
No 23 received a head injury and left for a HIA on 60 mins, replaced by no 8 (temp replacement).
On 71 mins 16 replaced 2 (substitution no 7)
On 72 mins 23 failed his HIA so that substitution became permanent (substitution no 8)
On 76 mins 21 replaced 9 (substitution no 9)
Is it the case that a permanent replacement of a failed HIA doesn't count as a substitution ? Or did Bath make a mistake ?
