This question specifically is about non-towered airports surrounded by round circles of E2 airspace, with one or more "extensions" of E4 airspace that abut the E2 airspace. Therefore it is not the same as the related question that may be noted above. Also the question noted above is about how certain airspace functions when the tower is open versus closed, not about why it is drawn a certain way on the sectional chart.
Note that this configuration-- a non-towered airport surrounded by a round circle of E2 airspace, with one or more "extensions" of E4 airspace that abut the E2 airspace -- is a somewhat unusual airspace configuration. In the vast majority of cases where a non-towered airport is surrounded by Class-E-to-surface airspace that has one or more rectangular projections, the entire Class-E-to-surface airspace is designated as E2 airspace. No E4 "extensions" are designated. Examples: KONP, KSHR. This question is not about that airspace configuration.
According to the FAA's "Airspace Designations and Reporting Points" document Order 7400.11C ( https://www.faa.gov/documentLibrary/media/Order/JO_7400.11C.pdf ) , KACV, KTLV, KSGU, KBIH, and KTPL all share the same airspace configuration: a round E2 circle around the airport, with one or more E4 "extensions".
Why then on the aeronautical sectional charts is the Class-E-to-surface airspace near KACV and KTLV depicted differently than the Class-E-to-surface airspace near KSGU, KBIH, and KTPL?
The first two are depicted with a dashed magenta circle going all the way around the airport, while the last three are not. In the case of the last three the charts give the impression that all the Class-E-to-surface near the airport may be E2, with no E4 "extensions".
KACV: California Redwood Coast Humboldt County near Arcata -- http://vfrmap.com/?type=vfrc&lat=40.978&lon=-124.108&zoom=10
E2 described on page E-127 of the "Airspace Designations and Reporting Points" document, E4 described on page E-211
KTLV South Lake Tahoe -- http://vfrmap.com/?type=vfrc&lat=38.894&lon=-119.995&zoom=10
E2 described on page E-135, E4 described on page E-220
KSGU -- St. George Regional Airport, UT -- http://vfrmap.com/?type=vfrc&lat=37.036&lon=-113.510&zoom=10
E2 described on p. E-84, E4 described on p. E-190
KBIH -- Bishop Airport, Bishop CA -- http://vfrmap.com/?type=vfrc&lat=37.373&lon=-118.364&zoom=10
E2 described on p. E-130, E4 described on p. E-211-212
KTPL -- Temple, Draughon-Miller Central Texas Regional Airport, TX -- http://vfrmap.com/?type=vfrc&lat=31.152&lon=-97.408&zoom=10
E2 described on on p. E-127, E4 described on p. E-209
It seems that it would be good for the chartmakers to standardize on the notation used at KACV and KTLV rather than the notation used at KSGU, KTPL, and KBIH, since there appear to be some functional differences between the E2 and E4 airspaces, as explored in the related question linked below.
Related question with links to additional related content -- What is the primary reason that the non-towered airports KACV and KTLV have E4 extensions to E2 airspace?