Yes, by convention when schematically drawing the strings of an instrument, the strings are drawn ordered top-down from the higher pitched to the lower pitched. So, in a drawing, the 1st string of an instrument is actually at the top and the last string (the 6th in the case of a guitar) is represented at the bottom.
As a mnemonic, if you know a little about music notation, remember that higher pitched notes go higher in the staff than the lower pitched notes.
That being said it would be better if 'top' and 'bottom' would be avoided to name the strings. The actual string number as per the convention of the instrument, or 'high pitch'/'low pitch' should preferably be used to avoid that confusion.
As a side note, the equivalent of 'treble' and 'bass' as synonym for 'high pitch' and 'low pitch' provide in some languages convenient short names, but I don't suppose that is common in English. However guitarists refer frequently the "high E" and the "low E" to name the 1st and 6th strings of the guitar, which is a rather convenient and unequivocal terminology.