There are several hundred titled photos in the album. How does one use the sequential feature?
exporting from Photos will turn your photos into files in a folder. The Finder or the program used to to show the photos will only see the file names. To keep the files sorted, include numbers into the filenames.
Photos can create filenames on export, that will start with a number, if you use "File > Export > export .. photos" and then set the option "Filename" to sequential, but this way the titles will not appear as part of the filename.
If you want to see the titles as the filename, you have to use "File > Export > export .. photos" with "Filename > Title".
To keep the sort order, include a padded running number in the title, so instead of "Statue of Liberty" as the title use "001 Statue of Liberty" as the first title. Photos has no tool to prefix the titles with numbers. You will have to do that manually or write an Apple Script.