Gosh LM that's a bit pooh (no pun intended)
Different trusts must have different rules...I was told 3 Botox then LIS...obvs once they saw how bad my fissure was I only had one and then the LIS
All I can say is the weeks before I had my LIS my pain was the lowest it had been just a burning no real spasms but I knew the fissure was still there and for me at least a slip up on diet could easily set it off. So I had LIS if I were you I would call him back and just bit the bullet there is really no chance of incontinence because like he said on the NHS they never cut more that 10% of the IS even if you beg plead and offer to sign papers they still won't cut more....yes I tried...also again your a male and you have no underlying issues so you should recover quickly.
Heck I have explosive liquid BMs and I have never had a hint of incontinence.
Good luck with whatever you decide I guess it's how much of an impact it has on your life