The 7.5.2 Exception was intended to allow players with eligible numbers to assume positions normally limited to ineligible numbered positions. It's reasonable to understand the language of the rule to suggest that these players, wearing numbers that don't match with their positions (lineman numbered 50-79) need to establish their role so as not to be confused with properly numbered interior lineman.
The Exception further requires that once these players assume those interior lineman positions, they are prohibited for becoming eleigible as a result of any shifting or changing formations. I'm sure some could (and likely would) argue what, "assume an initial position on his line of scrimmage between the ends" actually means, but it is certainly reasonable to interpret this as meaning, just what it says, that those players in the game by virtue of the 7.5.2 Exception must declare themselves as interior lineman by assuming an initial position on the line of scrimmage, between the ends.
If they have failed to do so, they are not complying with the basic requirements of the 7.5.2 exception rendering the formation illegal.
It seems this whole offensive strategy rides the line between legal and illegal, in any number of ways, and requires a level of precision execution that many teams will have great diffculty in complying with.
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