new hybrid commuter bike for someone who weighs 135kg

To be fair, the model that they offered would probably be less effort but I would question it's appropriateness solely as a commuting machine. I think some bike shop employees probably see a bunch of first timers coming in and buying a cheaper bike, which will be aluminium framed, and then finding it uncomfortable and blaming potholes and hard saddles. The Cobalt will probably mitigate a bit of that but you may not find it the magic bullet that they kind of make it out to be. Maybe they're hoping that you'll get on well with it and in a few years when your lighter and faster you'll come to them for a bike that it lighter and faster.

If you were to get a steel tourer on 35c tyres run at a decent pressure (80ish psi) a comfortable saddle that isn't too much of a sofa, perhaps some cycle shorts, and you pick your lines well on the road, you'll travel a bit faster and be pretty much as comfortable after a short period of conditioning. As for drop handlebars, they don't take too long to get used to. The added benefit for a larger rider is that they offer a range of hand positions including ones that will have less orthopedic strain.

Do try before you buy though. Even if you're trying out models and styles that are out of your price range. Evans do have steel road bikes in their catalogue. Take them out on a circuit that includes some up and down and tight corners. Make sure you're out for at least 15 minutes on each machine. You're buying something you're going to commute on, you want to make sure you're going to be comfortable as you'll spend quite a bit of your time on it. If after that you do want a hardtail then that's cool, you'll be making your own informed decision.