On QFX5k series switches, extended router data for sFlow is not supported. This KB provides detailed information on this.

On QFX5k series switches, when sFlow is enabled, extended switch data is included, but extended router data is not included.

On QFX5k models such as QFX5110 and QFX5120, the extended router data that would normally be embedded in sFlow packets is not supported.
Extended router data typically contains next-hop related information. However, this feature has not been supported since the initial introduction of sFlow on these platforms.
On the other hand, extended switch data is supported and is included in sFlow packets.
*QFX10k supports both extended switch data and extended route data for sFlow function.