No it is exactly one version ahead, the number is just bigger by 13. Firefox ESR 102 is based on firefox non-esr 102 and ESR 115 is based on non-ESR 115. There are no ESR versions in between.

As an analogy think of fedora and red hat

https://en.wikipedia.org/wiki/Red_Hat_Enterprise_Linux#Relat...

With that same scheme it would be red hat 6, 12, 19, 28, 34 instead of 5,6,7,8,9.

Thunderbird major releases match up with Firefox, in terms of dates and version numbering. However, Thunderbird releases major versions less often. Hence the discrepancy.

As I recall the team has been jumping the main/release branch by larger numbers as beta moves through more polish effectively making release the long-term servicing/ESR branch so 115 will start to be offered tomorrow.