David Lebovitz's Roasted Strawberry-Miso Ice Cream

Lebovitz also says churning the berries with the custard early in the process will result - because of high water content in fruit - in very soludly frozen berries by end of process.
Roasting or sauteeing the berries with sugar decreases the water content. That and adding them in later in process makes for a softer better texture of berries in final product.

His own preference.

If you read the article carefully as well as his replies in the comments section, he subtly reveals his preferences.

Without being explicit, he does not like fruit ice cream. For strawberries in particularly, he generally prefers them fresh. In one of his comments, he states that he prefers berry ices and sorbets over berry ice cream.

Additionally, he goes on stating that he might make the miso ice cream again and use the roasted strawberries as a topping. Clearly, he is not a fruit ice cream guy.

If he added the roasted strawberries while making the custard, he'd end up with a fruit ice cream which is something he does not prefer.

He knows that many enjoy fruit ice creams, he just doesn't count himself amongst them. But since he's no longer working in a restaurant kitchen and serving paying customers, he can do whatever he wants.

Fortunately, you can do the same yourself. You can either follow his instructions or modify as you wish.

Frankly, if I tried this out, I'd probably make the miso ice cream and keep the roasted strawberries on the side because my own ice cream preference is closely aligned with his.

Anyhow best of luck.