Xojo Chart lines straight on Desktop and curved on Web

[David_Cox]

I have a shared External Method for creating my Xojo Charts (ie code is identical). When I run the Method on the Desktop app (left), the Xojo Chart lines are straight, whereas on the Web app (right) the Xojo Chart lines appear curved.

There are other more trivial differences (2 decimal points, legend position, etc) which are OK with me, but is this straight/curving normal and expected?

[MarkusR]

one is not interpolated, xojo explains it is other source which just not have interpolation.
at least few years ago it was the case.