Browsers are the new OSes, so it follows that asking someone to only work with one or three tabs at a time, is like asking someone in 2010 to only work with one

Browsers are the new OSes, so it follows that asking someone to only work with one or three tabs at a time, is like asking someone in 2010 to only work with one or three applications open at a time. This is patently impractical, unless your specific task can actually be accomplished this way.