Unless this paper was applied to a very unusual surface, with a very unusual adhesive, I'd have to agree that these steps are somewhat "overkill" when the adhesive that might remain can be readily removed.
Once the paper has been stripped, follow up with wipe-downs using a sponge (dampened in a very warm water & white vinegar solution and rinsed often), and/or a moistened fine grade Scotch-Brite pad where stubborn areas need a little more coaxing.
After allowing the walls to dry for at least 24 hrs., pass you hand over them to feel for rough areas, which can be lightly sanded. Slightly moisten your hand or a paper towel & pass it over the walls; if it quickly comes up looking grimy, or your hand feels sticky or "gummy", then repeat the glue removal wash-down.
It's likely that the quotes you've received requiring the "extra steps" are being done honestly, with the desire to be sure their work can be guaranteed without problem, but a good cleaning of the walls should eliminate the need for quite so much in the way of base work.
If you expect to have one of these previous bidders perform the paint/finish work once you have cleaned walls, be sure to ask them first if the extra work you are doing will change their minds about requiring some of the steps they wished to take, as they may still insist upon doing them.