I would like to try to clarify some ' :)wildly inaccurate' statements/impressions often made/held about map accuracy.
All federal government maps for standard or principal needs have to meet horizontal and vertical accuracy criteria/tests. 'For maps on publication scales' ... of 1:20,000 or smaller (ie. 1:24k, 1:63,360, 1:100k, 1:250k, etc.) 'not more than 10% of the points tested shall be in error by more than 1/50 inch' - that is 40 feet on a 1:24k map and 167 feet on a 1:100k map.
Furthermore 'these limits of accuracy shall apply in all cases to positions of well-defined points only. ....' [I was once told by a USGS cartographer in Reston that the thinnest line that could be printed on paper was 1/100 inch]
Would not be much reason to use 32 sheets of paper for 1:24k's if they did not show more detail than a 1 sheet 1:100k. Except in special cases like a small over-edge area, the 1:100k's covered an area of 30 x 60 minutes; the 1:24k's were 7-1/2 by 7-12 minutes. There are edge and central tic marks showing the 4 by 8 array of 1:24k's. FYI - the 1:100k data was created by paneling the 32 1:24k maps. I never got a detailed explanation from USGS of the process; however, the 1:24k maps needed to be created first - this required the creation of those 20,000+ preliminary version (only a few of which went to final/standard maps).
No Assumption needed - a 1:24k has 4+ (100,000 / 24,000) by 4+ times the paper area available to show the same area of the ground surface and it's various features. IIRC at the time Garmin released the 1:100k mapset the only other topo product they were selling was 1:24,000 mapsets of individual National Parks on 3 CDROMS sold separately.
Only the hydro and transportation data was digitized (for the Bureau of Census). Garmin must have digitized the other types of features themselves or found other data sources. Boyd or anyone; have you ever over-layed the Garmin data on the USGS 1:100k DRG (digital raster graphic) images of the same area or compared it with the USGS 1:100k DLG (digital line graphs)? The USGS DLG files were in NAD27 and UTM coordinates - perhaps there was a glitch in the conversion process - I initially had some using GM when I created the Trails from USGS 1:100k overlay mapset.