1) first, you’ll NEVER notice a difference of 3IBUS. If you can you are a super duper taster. IIRC even the best tasters can’t tell the difference between 5IBU difference.
2) I would expect a difference as each developer will use a similar but different equation on getting their IBUS. For example one might think that you’ll get 100% of utilization from your hops, while another might think you’ll only get 90%.
My advice is to pick a program and stick with it. Brew and see what you have at the end. Then you’ll know if you need to back off on the IBUS or not on the next batch.