AMTEXT commands are provided as utilities for quick access to the most common text height creation. Why these 3 (3.5, 5, and 7) are chosen is because they represent 3 typical text objects defined in Object Property Settings (AMOPTIONS->AMtandards) that controlling layer, color, linetype and lineweight. BTW, you can change the text height during the command.
If you're looking for something more flexible, AMNOTE is probably the closest. It has a leader but can be turned off, and it works like any other Mechanical symbol text, react to scale area changes. If this still doesn't meet your requirement, can you send me an email at firstname.lastname@example.org for more discussion?
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