I thought it would be fun to post some other Bateleur tables done around the same time as the Conver, for comparison. I think you can see that other factors play into the legs issue besides perspective and placement vis a vis corners. Below is Lando left (c. 1760 Turin, Kaplan v. 1 p. 150), Burdel center (1751 Fribourg Switzerland), and for reference Conver 1760.
In the Lando, the tilting legs on the left contrast with the straight leg on the right, creating the impression of two legs on one side and one leg in the middle on the other side. The Burdel creates the impression that the leg on the right is in front, by the relatively wider spacing between it and the Bateleur's left leg, compared to the Conver, plus the lack of shading on the right, very straight up and down part of his leg. Also there is a line in the middle of the right leg, suggesting the possibility of another leg in back of it. The Conver, with narrower spacing but still the contrast within the leg, even a different color, is beautifully ambiguous.
Next, look at the Vieville left (c. 1650 Paris), the Noblet (Flornoy's "restoration," with its blue line which may or may not be in the original), and the Dupont (2nd half 18th century Brussels, Kaplan vol. 2 p. 330). The Dupont is typical of numerous Flemish-Belgian decks of the 18th century, the ones that have Captain Fricasee instead of the Popess. Vieville has a Popess, according to Kaplan. But the Vieville Bateleur's face and buttons resemble those of the Flemish-Belgian decks, suggesting a relationship.
Here the Dupont clearly does not have a table leg behind one of the Bateleur's legs. The narrow spacing between the rather phallic tableeg and the two Bateleur legs on either side excludes that possibility. The slanting leg on the right vs. the vertical legs in the middle create the impression that the fourth leg is beyond the left frame, and the length of the table creates the impression that it is in front. In the Vieville, a table leg might possibly be behind the Bateleur's leg, but the spacing, the table leg so close, suggests otherwise. So it is more like the Dupont. Noblet's, by the wider spacing, is more ambiguous.
In general, the more ambiguous cards are in decks that have proven, for whatever reason, to be the more popular decks after their own time.