If alkalines have more current capacity, available energy, then it would seem
logical to use alkalines. If you're selling clocks, you want to equip them with the
cheapest battery available.

I'm an expert in chemistry but not necessarily battery chemistry, so this is an informed but, not authoritative opinion.
Conventional carbon-zinc batteries have lower stability & more heavy metals, so I tuonk there has to be a convincing & irrefutable reason for avoiding alkaline.
I haven't purchased conventional batteries in probably 40 years, so every clock we've ever had used alkaline batteries.
I would never consider changing even for low demand electronics like a vlock.