here's the deal... from what i recall from the match several years ago...
and read carefully b/c right now i think you have some bad info from your deans which could screw up your match list
EM is one of the few specialties where there is 2 different tracks (straight vs. PGY2-4 format)
so, if you applied to PGY 2-4 programs, when you rank one of them, it will come with a supplemental rank list (for you to rank a PGY 1 program)... this supplemental list can be different for each PGY2-4 program. for instance, you applied to both BMC and Lincoln and you interviewed at a prelim in Boston and one in NYC. You would rather not move again. so when you rank BMC, your supplemental list would have PGY 1#1 choice as boston and then PGY 1, #2 choice as nyc.
you should only rank the prelim programs at the end of your match list if you would RATHER go into a prelim medicine track then try to scramble for an EM spot....
b/c if by some strange twist of fate you don't match at your top 12 choices, if you were left unmatched on "scramble" day... you would get a chance to scramble into an EM spot.
if you place a prelim spot 13/14/or 15th, you will likely match into one of them and then you will NOT be able to scramble into anything except for possibly an open PGY 2-4 program (which there are many fewer) ... you would have to do a year of prelim medicine and then reapply during that year...
if you do go the above route and rank the prelim spots 13 thru 15... and that's all you matched into... you will be notified on March 17th that you only have a PGY 1 spot-- you will however, NOT be allowed to scramble into a PGY1-3 or PGY 1-4 EM spot...
i would NOT rank the prelim spots on the main list (only supplemental list for the EM PGY 2-4 programs).... b/c even if you are unmatched and can't scramble for an EM spot, there will still likely be open prelim/categorical medicine spots... and you would be no worse off...
not to sound too critical but it's sad if the deans are giving you bad advice... unfortunately the match is a bit confusing and i got my best explanation regarding ranking prelims with PGY2-4 programs b/c i rotated at a PGY2-4 place as a medical student and was explained the above by the program directors at a PGY2-4 place...