That’s not what it is saying on the tourride website:
Tourride map
That shows you coming in from the north for the first lap (turning right over St. Michael’s Bridge for the extra loop), then on the final lap following the same stretch alongside the river from the north. On a Saturday that section of road beside the river is slow moving cars. To cross into Dock Park you then have to negotiate a 4 lane junction with traffic lights at the bottom of St. Michael’s Bridge. I tried adding in a streetview picture, but it kept reverting to the same picture you linked to.
The link you sent is the southern entrance into the park, according to the tourride map you don’t go on that road. Unless you have some kind of information pack that is different to the website!? Either way, it could be an interesting finish for tomorrow! Won’t be a problem when the road is closed next week, but take it easy tomorrow!