Fracarro website indicates it is a log periodic with gain of 10-11dBi (dB ref an isotopic radiator - a theoretical figure used to give a higher number) and that is over the entire old UHF bandwidth (21 to 69). That would be about 8dB ref a dipole (dBd which is a real world, measurable, number and the typical gain figure for any log periodic aerial).
So, that suggests to me, that your 4G filter was an extra device added to the system? Is this accessible to you? Can you remove it from the aerial cable easily? If 'yes' then please do so and repeat the signal level measurements and look for any reception problems.
4G filters are rarely needed. Only if in close proximity to a 4G transmitter, in a fairly weak signal location, and it is in nearly the same direction as the wanted transmitter. 4G would usually affect the highest frequency muxes in the absence of amplification overload... Which would be ch 59 from Pontop.
4G filters come in two flavours: rolling off above frequency ch 60, and above ch59. The 59 variety could well reduce the wanted mux level by a decent amount (oops) even though it is the correct one for Pontop Pike. For example,
Filter LTE 5...782MHz 59 channel | Televes has a loss of 6dB at the top end, cf 1dB at lower frequencies.
Do you know you are likely to suffer 4G interference? i.e. Have AT800 written to you? Have they supplied the filter? If no, then I see no reason to require the filter at all! (NB modern aerials are being designed to roll off above ch60 and/or have filtering included.. See the group T aerial on ATV's curves.)
NB Pontop Pike transmits ch58, 54 & 49 @ 100kW; ch 59, 55 & 50 @ 50kW (-3dB); ch 33 &34 @ roughly 34kW (-5dB) and local TV on ch 56 @ 5kW (-13dB).
I would expect all frequencies with the same transmit power should be roughly the same signal level, but there will be differences in the numbers due to the transmitted power levels, of course... and the additional effect caused by the 4G filter perhaps? Quality is usually more important the signal level per se. But I'd be happier to see figures of 60%+ wherever possible.
Check the levels on all received mux frequencies and post the results: with the 4G filter in circuit and again with the filter removed. This might show that the figures you have for ch49 (70) cf ch59 (44) are just how your TV reacts to the signal level presented... or not.
NB if the filter is not accessible (e.g. on the masthead), then you'll need to call back the installer to discuss removal... it can always be re-located to indoors should 4G interference be a real issue at your home. {If it's built into the antenna (aerial) now, in a design update, you'll be stuck with it - but the installer may still be able to do something to improve the signal level on ch59 if required.}