No -- multicolumn indexes are equivalent to compound indexes in RethinkDB.
RDBMSes don't need multi-indexing because they don't allow storing arrays of values in any meaningful way. Imagine having a row in a database that contains an array of values. For example, suppose that for every user you store an array of cities they've ever lived in. RDBMSes typically can't do that, but document stores can. If you'd like to efficiently find every user that has ever lived in Mountain View, multi-indexing lets you do that.
RDBMSes don't need multi-indexing because they don't allow storing arrays of values in any meaningful way. Imagine having a row in a database that contains an array of values. For example, suppose that for every user you store an array of cities they've ever lived in. RDBMSes typically can't do that, but document stores can. If you'd like to efficiently find every user that has ever lived in Mountain View, multi-indexing lets you do that.