Other diagnostic tools must be used to date these items.
Shape is more indicative of function - i.e., what the bottle was used for or contained - but even that has a myriad of exceptions.
In short, there was (and is) nothing to stop a glassmaker from using an obsolete method in the production of a bottle.3.
Some technological changes were expensive and not adopted by glass makers until it became an "adapt or perish" issue and many glass factories just perished.
An example of this is the finding of a few pontil scarred utilitarian bottles among otherwise late 19th or early 20th century refuse.
It is unlikely that this bottle was made during the same era, but instead was reused for a lengthy period or otherwise retained until broken or discarded.