Fair point. There are two points that are relevant.
1. Remember the individual hierarchies e.g. separation, level of noise etc. Remember that the hierarchy for "who the other people in the toilet are" starts with workshop participants (for the reasons you gave), then total strangers that you will not see again (e.g. motorways services, big shopping centres), then those few people you know whom you trust, then other friends, then colleagues at work who know you, continuing up to a rowdy group of drunk football supporters !
So you benefited from desensing with the first category. If you managed that OK, the next step is the second one on the hierarchy and not further up! So consider getting our to somewhere like a shopping centre, train station, motorway services etc.
2. You say "that the person next to you isn't judgemental". We emphasis on the workshop that:
- peeing is a total non-event and of no interest to guys who don't have shy bladder. Your being slow to pee is no more interesting than you being slow to blow your nose.
- that assumes they are noticing; for which we have endless evidence that they don't notice. One guy used to go wind-surfing with his mate. After the workshop he decided to tell his mate, saying that was why they had never peed together. His mate flatly contradicted him saying of course they had peed together. That showed the extent to which his mate had not noticed; he just assumed that they had.
3. Again we have lots of evidence that about 50% of guys feel uncomfortable in toilets especially when they are busy. These guys do not like standing next to someone and so look to have an empty urinal between them and anyone else; if not, they hang back and wait, or use a cubicle openly. So total strangers have their issues about personal space; i.e. don't try to stand next to someone - instead give yourself space.
It is common to struggle after a Beginners workshop. Guys benefit from returning to a Follow-up workshop where they can share their experiences and move forward, in your case by hitting the public toilets and dealing wont total strangers. One step at a time.
Hope that helps