The "left-handed" musicians (and people) that I know are not 100% left handed (hence the quotes). For example, my nephew writes with his left hand but plays violin right-handed and uses a computer mouse in his right hand. Other musicians I've known both write and play "left handed".
In short, my experience is that there is an overall misconception about handedness in that it is binary and applies to everything. While most people do everything right handed, I know many people (including myself) who do some things with one apparent handedness and other things with the opposite handedness.
I disagree that drumming is ambidextrous. Hi hat and snare techniques are different, and usually they are played at the same time, so players of drum kits will have one hand trained for the hi hat and the other hand trained for the snare.
If I were in your situation, I would work with the student as early as possible in the process to get to the bottom of whether they feel at all more comfortable one way or the other. They might naturally feel more comfortable playing right handed, or they might not care one way or the other. If they feel more comfortable with a left handed setup, I suggest you may do them a great disservice by teaching them to play right handed instead.
It may seem like a lefty drummer will have a disadvantage in kit setups, and there is a little bit of truth to this. When I stage managed a festival where our target changeover time was five minutes (!!), we had a few lefty drummers come through and we knew we would not be able to switch the kit right to left in such a short amount of time. So that was inconvenient, but that is an unusual situation.
Every other situation I've been in, the drums are personal enough and setup time is reasonable enough that lefty drummers have basically had the same amount of work to do as righty drummers in terms of setup. Bass players don't seem to have a consensus on whether they generally prefer hi hat side or floor tom side of the kit, so that's not an advantage or disadvantage either.
Finally, unlike guitars and basses, there is no special equipment for left handed drummers - it's all the same gear, just set up differently. So there's no disadvantage there.
So pros of a lefty setup for lefty drummers is they are more comfortable and likely will learn faster and enjoy it more. Cons are virtually none. While pros for righty setup for a lefty drummer are virtually none and cons are the exact opposite of the pros for a lefty setup.
Find out this particular student's particular preference and honor it. If they have no preference, go righty.