Eh...
... we have to maintain a bit of historical and sociological perspective; in those days, modern science was infant-new and the old classical classifications were, though not in name, but in practice, smashed.
Einstein, Bohr, Lewis, Debye, Orgel, etc. were all doing some chemistry, some physics, some applied mathematics. A whole new vista had just philsophically opened up and they were exploring it. Were they chemists or physicists? I'm not at all sure THEY cared too much. A lot of these designations had more to do with where they worked rather than what they did.
There is, however, no mistaking that they made giant contributions to both fields.