Experimenting with different tools so probably why it ended up being a bit longer than the solution. The solution is definitely more optimal but I guess there is many ways to Alteryx complaints.
Some lessons learnt that I thought I'd share with you from my experimenting: I noticed that the summarise tool explodes the memory of the bucket to a ridiculously large variable string. I noticed no optimisation was performed in the solution. So, I have used a select tool purely to optimise memory early. The main reason why my solution is longer is due to using split to columns and a formula tool to extract matches instead of split to rows. It would have saved me time cleaning up the commas at the end too.