[mandarg]

Having learned multiple Devanagari languages at school (including both Sanskrit and Hindi), I don't recall being explicitly taught stroke order as such. There's an intuitive way to write most Devanagari characters that usually corresponds to the "preferred" order you mention, which is only apparent in serif Devanagari fonts anyway. But for example, I have no idea what the preferred order is for U+0918 घ, and never learned one as such.

Side note: since you mentioned ballpoint pens, (at least 10+ years ago, things might be different now) we weren't allowed to use a standard ballpoint pen/biro; fountain pens were preferred and micro-point ink or gel pens were allowed.