The first round of stock buybacks and the convertible notes occurred under the last CFO. So the new CFO is following the precedent which is likely set by the board and Helen.
I agree that the convertible notes are unnecessary and are eventually dilutive. But when combined with stock buy backs, they are a way of rewarding the current shareholders from the future earnings/growth.
Halo is not alone. Look at GMAB. They did the same. Issued warrants and bought back shares to offset the dilution.
The difference is that they explicitly stated in their press release that they are offsetting the dilution.
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