Of course you're correct. But outlawing the sale of only new fluorescent fixtures, rather than the bulbs, would be a much less disruptive means of eventually achieving the same result, without forcing immediate costs onto every property owner.
If the sale of new fixtures were banned, the demand for bulbs would diminish over time, to where finally the bulb pricing increases to the point where the last few stragglers convert. But in the majority of cases, the aging-out of old fixtures and ballasts would have most already converted, long before the bulbs ultimately went NLA.