I tend to agree with Homer.
The majority of Alex Henry falling blocks I've seen in person, print or online do not have sling eyes on the barrel or stock so I think the tie on sling is very likely.
Of course, many rifles with the notched forend do have eyes as well so I suppose the hunter could have their choice of sling attachment.
Generally, these rifles (450s & 360s anyway)were meant for stalking in the British Isles and one wouldn't want any noisy sling swivels clacking on the barrel while approaching their quarry.