I agree this is purely an academic discussion and should have little tax effect, if any at all, since it is likely that eligible educators are mostly maxed out on the $250 limit even without taking these expenses into account.

I am also less concerned about the phrase "in the classroom" but more about what categories of expenses may be deductible.

In the JCT report for Job Creation and Worker Assistance Act of 2002, under which the provision was created, the word "classroom" only appears in the subject heading "F. Deduction for Classroom Materials".  Again, when this provision was amended by the Education Tax Relief Act of 2015, the JCT report cited the "Committee recognizes that many elementary and secondary school teachers provide substantial classroom resources at their own expenses" as the reason for the change.

There is no mention within either JCT report that "classroom" should be a criterion for the deduction.  In any case, it would be unrealistic to restrict qualified expenses to those that are incurred "in the classroom" as many of these expenses are incurred while eligible educators are at home (e.g. computer equipment and subscription for software) although the materials produced would ultimately be used inside a classroom.  It would, therefore, be more reasonable to interpret "classroom" as being a setting instead of a physical structure.

The JCT report of 2002 makes clear that congressional intent was to ensure that "ordinary and necessary business expenses" otherwise deductible under §162 and subject to the 2% floor may be deductible above-the-line by eligible educators.  Rather than liberalizing the deduction based on §162, the Congress confines the deduction to only those specific categories of expenses outlined in the current subparagraph (a)(2)(D)(ii).  In fact, Congress found it necessary to expand these categories of expenses to include costs of professional development with the enactment of the Education Tax Relief Act of 2015.

If Congress had intended for §162 to govern what may be deductible under §62 for educators, there would have been no need to specify what expenses may qualify when the provision was first introduced and subsequently expand that to include costs of professional development.

If the question is whether cell phone calls are deductible, I would be inclined to say no, not because these are not legitimate expenses under §162 but because these do seem to fit the specific categories of expenses outlined under §62(a)(2)(D)(ii).