If it's a 3 year course @crazycrofter then for the Easter type spring tasters he would need to apply this year, so he's right with what if he's doing.
But, if he doesn't get one, he can continue to apply next year for that year's summer internships under the 'penultimate' year, these then can lead to an returners offer upon graduate, invite to assessment or a further final year internship before decision, they all cary so much.
Then there's the applying in the final year as an UG, where judging from DD's UK friendships groups, they have the most success of getting invited to the respective processes. As an example, before DD had heard back on her returners offer early last month, she applied to 2 top tier consultancy firms and one major multi brand org and got through to the testings and beyond, where as last year applying to the same businesses she got auto rejected within hours/days.
Finally the applying as a grad. Looking at the openings dropping into the recruitment portals now, they are there, though to @Shimy's point, the roles will be where the remainder opportunities lie, not already taken with the early bird students via the internship/placement routes. I don't think this is a bad thing, businesses are just more cautious with not taking on volumes of the past due to market conditions.
Your boy is very driven, and so long as he gets a spreadsheet up so he can log what he's applying for and the deadlines etc then he'll be grand. My point is that he needs to get stuck into his course too and in this climate of negative noise it's easy to panic.
Apologies for the over explaining, I got very confused with the timelines early on with DD, but knew she didn't want to go into a masters so we got our heads into it like your son is.